[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/Roman_Legion_Carpe_Diem_6212.jpg]]
[[caption-width-right:350:"Cross the river and go to Rome! [[GratuitousForeignLanguage Alea Iacta Est]]!" Hey, wait a minute. [[CaptainObvious Something here does not seem right...]] [[note]]A-ha! [[ComicallyMissingThePoint That stenciling is using Arabic numbers, not Roman numerals!]][[/note]]]]

->"''...we now live in a world where kings and noblemen rule the roost. And they've turned all of central Europe -- '''our home, now, ours and our childrens' to come''' -- into a raging inferno. We are surrounded by a Ring of Fire. Well, I've fought forest fires before. So have lots of other men in this room. The best way to fight a fire is to start a counterfire. So my position is simple. I say we start the American Revolution -- a hundred and fifty years ahead of schedule!''"
-->-- '''Michael Stearns''', ''Literature/SixteenThirtyTwo''

The problem with the past is that it's so uncivilized, but any time traveler worth their salt can fix that. Just introduce it to the delights of modern technology, several centuries early. You may need to go through a few intermediate stages, replicating the history of technology on fast forward, but you know exactly what needs doing. How difficult can it be?

There are two types of time travelers who try this stunt - the unwilling ones, TrappedInThePast with [[StrandedWithEdison just the right skills needed to jump start the industrial revolution]], and the reckless ones who don't care about paradoxes, they just want to rewrite history for the better.

Either way, this is a long term plan. Even optimistic heroes will expect to take a few years to get the desired results. Realistic ones will consider it a lifetime's work. The hero can't leap straight to modern technology; [[TechnologyLevels they have to get the past society to go through all the intermediate steps first]], or they won't have the necessary tools to make the tools to do the job. As such, this is typically the plot of an entire book, or even a series.

AncientAstronauts and explorers rediscovering [[LostColony lost colonies]] occasionally fall into the trope, if the story goes into detail about how they introduce technological advances, but they normally gloss that over. By contrast, works in this subgenre typically go into great details about the new technologies being introduced to the past, and their social impact, as well as addressing all the problems that would realistically crop up.

If the stranded party has a phone to a high-tech society, whether in the future or on another world, this trope can still apply. The phone can provide them with all the information they need, but they still have to deal with the immense practical problems involved in getting from medieval to modern technology. It would still take decades to get 14th century England from church bells to digital clocks, even with an internet connection to the present day, and the full resources of the kingdom at your disposal. However, if the stranded party can get actual physical objects from their high-tech friends, the difficulties melt away, and this trope does not apply.

If a Hero succeeds, there's still a risk of [[GoneHorriblyWrong going horribly wrong]], [[GoneHorriblyRight going horribly right]], or both.

FridgeLogic would dictate that this would result in an infinite technological loop: Suppose the radio was invented back in 50 B.C. by a time traveler. Since this means that time travel is possible, eventually somebody from the future of the timeline created by the original time traveler would travel back to an even earlier time (for example, 800 B.C.) and give radio to the Akkadians or something. Then a time traveler from ''that'' timeline would introduce radio even father back, repeating until the very first generation of humans ever to evolve is given advanced technology and civilization.

!!Compare with:
* ETGaveUsWiFi: Essentially, this trope from the POV of the less developed culture.
* LowCultureHighTech: Will result if the time traveler ''doesn't'' lay the groundwork for the low tech people to properly replicate the future tech.
* TimelineAlteringMacGuffin

!!Contrast with:
* ThisIsMyBoomstick: The Hero only wants to impress the locals short-term.
----
!!Examples:

[[foldercontrol]]

[[folder:Anime and Manga]]
* Basically the background of the Zaibach Empire in ''TheVisionOfEscaflowne'': Emperor Dornkirk (who was [[spoiler: in this reality IsaacNewton]]) brought the gift of science, culture and technology to the weak, incompetent farmer-nomads of the Zaibach area in Planet Gaea, developing themselves into a force able to defend themselves, eventually build their own industrial civilization, and eventually turn into a warmongering empire.
* In MaoyuuMaouYuusha, the Demon Queen, a peace-seeking sort despite her name, consorts ([[ArrangedMarriage literally]]) with the opposing Hero to bring modernizations to farming, industry and navigation that help humanity avoid the need for war. Expected pitfalls are expected by the GenreSavvy leader as not everyone on either side of the war is willing to cede control over those who once lacked control of their destinies or did things that others expected because of their heritages.
[[/folder]]

[[folder:Comics]]
* The ''{{Marvel 1602}}'' mini-series has a time-displaced CaptainAmerica sent back to Elizabethan times. When asked to return to the future, he insists on staying to try and build a better America from the beginning -- which he does in small ways, such as helping a group of colonists survive a winter that should have wiped them out, or warning the natives against selling their land to unscrupulous capitalists. The final touch comes when, because of his actions, the American colonies declare independence from Britain 174 years early.
** And it's got ''[[EverythingsBetterWithDinosaurs dinosaurs]]''.
** It also has consequences beyond his control -- his presence causes the MarvelUniverse to impose itself on the past, and period versions of the Comicbook/{{X-Men}}, [[Comicbook/TheAvengers Avengers]] and other superheroes start appearing.
* This is the premise of Jonathan Hickman's ''ComicBook/PaxRomana''. The ailing Catholic Church sends a paramilitary group back to 312 AD to use both advanced technology and knowledge of future events to help the Roman Empire set up a stronger foundation for the Church. Things don't go as planned, but even so, technology and culture advance much quicker than in the unaltered timeline, giving rise to a utopian society.
* The Argentine comic ElEternauta (second part): the protagonist decides to give to a tribal AfterTheEnd civilization of the future, enslaved by an alien race, knowledge of modern weaponry and machinery. Since the available tools and labour skills are quite crude, they can't go beyond mid-XIX century tech: simple pistols, muskets and cannons and basic steam engines (making it a SteamPunk comic in 1976).
* One ''ComicBook/WhatIf'' story (in v1 #33) featured Tony (ComicBook/IronMan) Stark becoming trapped in the time of KingArthur. He starts advancing the technology level singlehanded till he can recreate his Iron Man armor.
* In a ''Tim Traveller'' story, Tim is annoyed that his dad doesn't get modern technology, so decides to remedy it and goes back in time to show his laptop to some cavemen. They don't understand it and just try bashing it, which leads them to invent fire.
* In the ComicBookAdaptation of ''Series/ItsAboutTime'' the astronauts build a giant mousetrap to trap a giant rodent. How they managed t smelt the metal used in the thing isn't brought up.
[[/folder]]
[[folder:Fanfic]]
* ''FanFic/SarumanOfTheManyDevices'' The basic premise is this - the titular character aided by a rather benevolent AI introduce renaissance-era technology, including fairly advanced steelworking and of course guns to Middle Earth in an attempt to bring forth an industrial era. Specifically, to the Uruk-hai working for him already.
[[/folder]]
[[folder:Film]]
* ''Film/CrusadeInJeans'' had TheHero do this too, by using the assembly line principle along with an Ipod to bribe the baker to bake a lot of bread overnight.
* ''ThePhiladelphiaExperiment II'' combines this with SetRightWhatOnceWentWrong: A stealth aircraft armed with nuclear bombs is accidentally transported back in time to Germany in 1943, where it's captured by the Nazis and used to bomb several cities in the eastern United States (including UsefulNotes/WashingtonDC), with the end result that the Axis Powers won UsefulNotes/WorldWarII. Needless to say, the protagonist from the original movie is the one who winds up having to fix this mess.
** This is combined with ''LowCultureHighTech'' when the aircraft is destroyed on its final run. The Nazis, of course, want another and the scientist who claimed to have invented it can't replicate one. In the revised history, his son trying to clear the family name.
* ''{{Sengoku jieitai 1549}}'' (also known as ''Samurai Commando: Mission 1549'') features failed experiment which leads to time travel of a wounded samurai to our times and a group of soldiers to the year 1549. When the second group of soldiers goes to 1549 in a search and rescue mission they discover, among other things, a refinery.
* Minor example in ''NightAtTheMuseum''. Larry accidentally left behind his smartphone back in post-WWII United States (specifically, VJ Day), and a passing seaman picks it up, takes it home, and takes it apart. The seaman's name? Joey ''Motorola''.
* PlayedForLaughs in ''Film/HotTubTimeMachine'' - one of the characters decides to stay in the 1980s instead of returning to his present, and spends the intervening time becoming a billionaire by getting in on the ground floor of every important innovation since between then and now.

[[/folder]]

[[folder:Literature]]
!!! One person
* ''Literature/AConnecticutYankeeInKingArthursCourt'' is one of the first works to use this trope [[UnbuiltTrope or to seriously examine the difficulties behind it]]. The aforementioned Connecticut Yankee attempts to introduce both modern technology and [[ValuesDissonance modern egalitarian ideals]] into a medieval feudal Camelot, but events spiral out of his control and cause the timeline to snap back into course.
* Creator/PoulAnderson [[{{Deconstruction}} showed the problems]] with this in his short story ''The Man Who Came Early'', in which an American soldier stationed in Iceland is sent back to the Viking Era after being hit by lightning. Luckily the Icelandic language has not changed much since then. All his attempts to change history fall flat on their face. When he tries to show the Vikings how to make compasses, he has no idea where to find or mine magnetic ores. When he tries to show them how to build more modern sailing vessels, the Vikings point out that such vessels are too cumbersome to dock anywhere where there is not a ready built harbor, an obvious rarity in that time period, and so on. The story's main point is that introducing future inventions is immensely difficult because most advances are useless without an advanced societal infrastructure to support them.
** Also his contribution to Creator/HarlanEllison's ''Literature/DangerousVisions'', "Eutopia", is about an alternate world where Alexander the Great solidified his Empire and the Greeks are still ruling the world in 1960 AD (or thereabouts).
* Happens ''InSpace'' in the Larry Niven novel ''DestroyerOfWorlds''. A lone Pak (a highly intelligent, super strong, long lived creature) gets stranded on a primitive world. He introduces the natives (who have Bronze Age technology) to technology in steps, hibernating for unknown periods between each step. He needs to do this to escape the primitive world, by reaching the ramscoop level.
* ''The Cross Time Engineer'' and sequels by Leo Frankowski. Polish hiker Conrad Schwartz, in a drunken stupor, bypasses all kinds of security and stumbles into a historical-research time portal (created, coincidentally, by his cousin) and awakens in thirteenth-century Poland, where he has just ten years to industrialize and unite his nation before the Mongol hordes arrive and kill ''everybody.''
** This one has been [[http://community.livejournal.com/canon_sues/94852.html accused]] of being one big bit of MarySue-starring wish-fulfillment. Bad enough the original publisher dropped him so the later novels are self published.
** Language difficulties are {{hand wave}}d in a justification that "all Slavic languages are pretty much the same." Diseases don't really rear their head until the 6th and self published book, ''Conrad's Quest for Rubber'' where they have to deal with unfamiliar diseases in Africa, but is semi-justified by Conrad's cousin going back in time to make Conrad sterile (no, not like that... he's rather prolific, really).
** It does not help that the author 'cheats' by having the time traveling cousin provide Conrad with all sorts of help that makes Conrad way more effective than he should have been and saves his life when Conrad's actions are about to get him killed.
** An alternate timeline is mentioned where one decision by Conrad from the first book changed the outcome of everything. The alternate Conrad failed to get the patronage of a powerful lord and was not able to accomplish anything on his own.
* Inverted in ''The Centurion's Empire'' by SeanMcMullen, the premise of which is that AncientRome developed a medicine that [[HumanPopsicle allowed the human body to survive being frozen]], and promptly started storing its best and brightest. After the empire collapsed the one survivor set up shop in an English village, being unfrozen when they needed his military expertise.
* In Creator/TerryPratchett's short story ''Once and Future'' a {{time travel}}er called Mervin finds himself not only trapped in the past, but in a past that never existed; the AnachronismStew that was KingArthur's time. Working as a doctor for a village in Sir Ector's demenses, he quickly realises that what they need is a great and noble leader, gimmicks up an electromagnet to hold a sword in a stone, and waits for a candidate whose body language suggests he's sensible enough to take advice. It works, although not quite how he expected.
* Nimue Alban's situation in Creator/DavidWeber's ''Literature/{{Safehold}}'' series lacks time travel, but otherwise fits perfectly. Nimue (or rather a RidiculouslyHumanRobot with her personality) is awoken in the last human world of Safehold, which has been trapped in MedievalStasis for almost a millennium thanks to its [[AGodAmI delusional]] founders. Nimue's objective is to undo this and bring humanity back into the era of space travel. Many details listed in the description are averted, since robots can't get sick, and Nimue has to learn Safeholdian English before she can venture out among its people.
** For those who don't get the joke, she switches from the name Nimue Alban (Nimue as the lady in the lake, and Alban as in England) to Merlin.
*** Alban is the Gaelic form of Scotland, England is Albion (and it's in French)...
** Merlin/Nimue is aided in this task since this was planned out rather thoroughly and included a library computer, some advanced equipment and a limited manufacturing capacity. Of course there was also the unexpected bonus of [[OneManIndustrialRevolution Baron Seamount and Edwyrd Howsmyn]].
* ''Literature/LestDarknessFall'' by Creator/LSpragueDeCamp. Martin Padway is struck by lightning and finds himself in sixth-century Rome, on the verge of its ruin at Justinian's hands and the onset of the Dark Ages. He may be able to save civilization, if he can only get the ruling Goths to grasp the ''value'' of his innovations. Notable as it does take a few tries to figure out what does and does not work...
** Also notable in that one of the first and most important inventions he introduces is brandy. In itself, useless. For making money and building a place in society, invaluable.
* Brought later full circle with ''To Bring The Light'' by David Drake, which is bound with ''Lest Darkness Fall'' in some editions. In this story a woman from Justinian Era Rome gets sent back to the founding of Rome and must use the inventions of later Rome to help found it...
* As a TakeThat to ''Literature/LestDarknessFall'', Creator/FrederikPohl wrote the short short story "The Deadly Mission of Phineas Snodgrass." Snodgrass gives the Romans modern medicine and agriculture…but not birth control. Oops. The exceedingly overpopulated alternate timeline he created decides to do something about it. For added fun, it explicitly mentions the de Camp story.
* Temporally inverted in Philip Francis Nowlan's ''Armageddon 2419 A.D.'', or as it's better known, ''BuckRogers in the 25th Century.'' Rogers, in the various versions of his tale, brings lost knowledge and a certain 20th-century vitality to future America and/or Earth as a whole.
* ''Lord Kalvan of Otherwhen'' by HBeamPiper. Pennsylvania cop Calvin Morrison runs afoul of the Paratime Police and is accidentally transported to a medieval alternate Earth where a corrupt theocracy controls the secret of gunpowder. Pretty realistically handled -- he knows the basic formula, but also knows that there were steps in making it consistent that he needs to rediscover, and he has to convince wary leaders to build up the entire infrastructure for gun manufacturing from scratch.
* HarryHarrison's ''Deathworld 2'' features a non-time travel version of this, in which interstellar adventurer Jason dinAlt is stranded on a LostColony which has regressed to barbarism. Various bits and pieces of more advanced technology, generally regarded more or less as sorcery, are held as closely guarded secrets by the different clans (one group still knows how to make primitive petroleum-fueled engines, another how to make some crude electrical devices, yet another clan practices alchemy-level chemistry). The hero winds up completely revolutionizing the planet's backwater society solely out a desire to get off that primitive dirtball and back to someplace more civilized. The language issue is avoided as everyone on the planet speaks a (somewhat degraded) version of Esperanto.
** In one of HarryHarrison's ''TheStainlessSteelRat'' novels, the main character ends up in a pocket universe that contains an alternate version of the Napoleonic Wars, in which the BigBad gives Napoleon 20th century artillery. Napoleon, already an artillery genius, uses the technology to easily beat all of Europe into submission. The main character has to explain to an English nobleman the mechanics of one such cannon, who then uses it to sink a ship with a few shots.
** Interestingly, Jason manages to make working engines despite claiming that no one knows how internal combustion engines work anymore.
* ''The Other Time'' (started by Mack Reynolds, completed by Dean Ing after Reynolds' death) features a modern day (1980's) anthropologist doing field work in Mexico who gets thrown back in history to just the right time to run into Cortez and the conquistadors. The language issue is avoided as the hero (being an anthropologist) naturally speaks Nahuatl and Spanish.
* HarryTurtledove, ''Literature/TheGunsOfTheSouth'': Time travelers from the near future supply modern guns to the Confederates during the US civil war.
** The computer engineer among the "Rivington men" of ''The Guns Of The South'', who says that if and when the computers they brought back to Confederate America break down, he won't be able to fix them, because the time period doesn't have "the tools to make the tools to fix them, and probably a few iterations after that." Reproducing AK-47s though, is within their grasp (see Afghani copies of the AK-47 made in the 1980s).
** Also something of a {{deconstruction}}, with the Rivington men outright telling the Confederates (at least prominent ones like Robert E. Lee and Jefferson Davis) that they're time-travelers, and then the Southerners successfully defeating them despite their technological superiority when they turn against them.
* ''Literature/BelisariusSeries'': Two factions from the far future, one attempting to make a future hostile to transhumans, the other trying to save a tolerant future. Neither the future that was, nor the future if TheBadGuysWin happen, as a new GoldenEnding happens significantly different than ours.
* ''Literature/TheHitchhikersGuideToTheGalaxy''
** In ''Literature/TheRestaurantAtTheEndOfTheUniverse'', Arthur Dent attempts to prompt the evolution of the human race by teaching the primitive humans how to play Scrabble.
** And he later tries to modernize the Lamuellans. The only invention he succeeds in introducing is the sandwich. They take it very seriously, though, and Arthur's position of divine sandwichmaker gets him even more respect than the village chieftain.
*** A bit of a Deconstruction: Arthur doesn't know ''how'' to make anything but sandwiches. Because Arthur is the consummate average man, he doesn't understand most of the technology he's familiar with. If you were in Roman times, could ''you'' make a digital camera? Thought not.
* John Barnes's Timeline Wars trilogy: ''Patton's Spaceship'', ''Washington's Dirigible'', and '''Caesar's Bicycle'' all see this trope used, as part of a multi-universal time war against Carthagian descended timelines.
* Creator/IsaacAsimov's short story ''The Red Queen's Race'' is about a man who attempts to do this to ancient Greece, sending back modern knowledge with the intention of getting the scientific revolution going in classical times and giving the world a two-millennium head start. [[spoiler:However, the professor who did the translation into ancient Greek realizes what was up, and so deliberately included only such information as would explain certain before-their-time theories that really did appear in ancient times, thereby creating a StableTimeLoop.]]
* A variation from K.A. Applegate's ''{{Everworld}}'' series: the heroes, while trapped in a FantasyKitchenSink alternate world, introduce telegraphs to an Elven city, and use the technology to get rich.
* {{Conversed|Trope}} in Kir Bulychev's short story "Паровоз для царя" (lit. Steam locomotive for the tzar), where the characters discuss how hard would it be to pull this off in RealLife: if you were to give the tzar the technology of automobiles, you'd first have to explain to him the workings of petrochemistry (assuming he'll listen to your ramblings at all). Oh, and you'd better be an expert in petrochemistry and engineering in general.
* In Creator/VernorVinge's ''Literature/AFireUponTheDeep'', two groups on a medieval planet get technological advice, but not physical help, from stranded human children with, respectively, a small computer and an FTL phone, allowing them both to advance significantly. It helps enormously that the child's computer has a full history of technology stored, while the people on the other end of the phone can look up theoretical academic research on bringing technology to lost colonies, which is apparently a minor academic discipline in that galaxy.
* Referenced/averted in 'The Golden Crown'- Maegen decides that radios would be useless, and brings mini chocolate bars and ball-point pens to trade to the Romans instead.
* A very short story ''Ask Caesar'' by Yevgeny Lukin and Lubov Lukina is an attorney's speech in court. His client is accused of attempting to change history by teaching modern science (up to quantum physics) to Cro-Magnons. "But did it change anything? No." Except for some insignificant details, like the fact that Gaius Julius Caesar has been diced with lasers.
* ''Literature/DoctorWhoNewAdventures''
** In ''Just War'', an incautious time traveller accidentally gives the Nazis a technological leg-up, resulting in them developing stealth bombers in time for World War II.
** In ''The Room With No Doors'' [[spoiler: Joel explains to a 17th century Japanese warlord how to turn a loom into a calculating engine. He's surprised at how quickly the warlord catches on, and comes up with uses for computers that Joel thought he'd have to lead up to.]]
* A fantasy version is introduced in ''Literature/GuardiansOfTheFlame'' where Lou Riccetti's wizard character renounces his magic only to start using his engineering knowledge to overturn MedievalStasis in their fight against slavery. Predictably, the opposing factions, although not privy to the details of things such as how to make gunpowder, find ways to adapt the technology through magic.
* ''Literature/TimeScout'': Sort of. One downtimer gets his hands on uptimer materials and eventually discovers his way through the gates to La La Land.
* In the Literature/DoctorWhoNewAdventures novel ''Just War'', an incautious time traveller accidentally gives the Nazis a technological leg-up, resulting in them developing stealth bombers in time for UsefulNotes/WorldWarII.
* The first book of Alex Scarrow's ''Literature/TimeRiders'' Series has a man intentionally travel back to 1941 a) to give Hitler a ton of future tech, b) to convince Hitler not to invade Russia and c) to take over Nazi Germany himself. In the end, German steamrolled most of Europe and a good deal of the USA in twelve years, with Russia and China next on the schedule. Hovercrafts and pulse rifles tend to give you an advantage. Did I forget to mention the guy did this ''intentionally''?

!!! A group or community is transplanted.
* ''[[IslandInTheSeaOfTime The Islander Trilogy]]'' by SMStirling. The island of Nantucket is whisked into 1250 BC, and must contend with Bronze Age cultures and their own crop of power-hungry renegades. This one ''does'' contend with language difficulties, uptime diseases, and so forth; the Nantucketers manage to wipe out huge numbers of Native Americans before they even realize what's going on, because the first party sent to the mainland contains someone with a sniffle. Their language difficulties are moderately eased by the fact that the languages of Europe are, at that point, much closer to still being "Proto-Indo-European"...
** Also helped by Nantucket being big and upscale enough that having a professor of ancient languages on it at the time isn't ridiculously improbable.
* The ''Assiti Shards'' milieu by Eric Flint and others. Cast-off shards of transdimensional alien "art" bombard Earth and transpose large chunks of it with other times and places. Several alternate histories are planned in this meta-setting, including ''Time Spike'' (several separate Shard events deposit a modern maximum security prison, the Cherokees on the Trail of Tears, a band of conquistadors, and multiple pre-Columbian Indian settlements into the Cretaceous), ''1776'' (the armies of George Washington and Frederick the Great both find themselves in ancient Rome during the Crisis of the Third Century), and ''By Any Other Name'' (the Assiti themselves make unwilling contact with Elizabethan England), but only two have seen any publishing. The first one has, however, seen a lot:
** ''Literature/SixteenThirtyTwo'' and many, ''many'' sequels. The West Virginia coal-mining town of Grantville is translocated to southern Germany in the middle of the UsefulNotes/ThirtyYearsWar, utterly shattering the power structure and world view of Reformation Europe. Once again, this setting deals with language and diseases fairly well. Although in this case, it's the ''uptime'' people of Grantville who have to worry about the risk that the pandemic plagues of the 1600s will devastate their community. On the bright side, they're at a recent enough point in the past that their English is recognizable in England, and their German-speakers are understandable to the Germans around them.
*** In many ways, the real shockwave comes from the introduction of modern ''political'' ideas such as egalitarianism and religious tolerance. One major player in the setting is the Committees of Correspondence, an international organization made up almost entirely of downtimers devoted to promoting democracy, freedom, and sanitation across Europe. They look something like a cross between the Sicilian Mafia and the Sons of Liberty.
* Parodied repeatedly in this [[http://subterraneanpress.com/magazine/winter_2007/fiction_missives_from_possible_futures_1_alternate_history_search_results_b short story]] (scenario 6).
* The ''Literature/AxisOfTime'' trilogy by JohnBirmingham. ''World War 2.1: Weapons of Choice'', ''World War 2.2: Designated Targets'', and ''World War 2.3: Final Impact''. A multinational naval task force from 2021 is sent back to UsefulNotes/WorldWarII, where it (literally) impacts with the American fleet steaming for Midway. The consequences are ''extremely'' far-reaching.
** And there's even a nod to ''The Guns Of The South'' in that while the up-time multinationals can easily reproduce the AK-47 and "low-tech" (for the early 21st Century) gear, their more advanced devices can't be duplicated because the composites, chemicals, or specific materials can't be manufactured with 1940s-era equipment.
*** Not just the uptimers. The Soviets manage to do the same by studying [[spoiler:the databanks aboard the ''Vanguard'']]. The Nazis and the Japanese also make some small advances, but not many.
*** Also, the American and British versions of the AK-47 feature underslung grenade launchers, making them much more effective in combat. By the third novel, all the uptimer ships and troops are forced to "downgrade", as their ammunition has run out. This "downgrade" is still superior to what was available in the [=1940s=], though. They've been able to reproduce the fuel mix used by ships, though.
** A somewhat similar story can be seen in the manga and anime {{Zipang}}. A good chunk of the plot is about whether or not to give the metaphorical radio to the metaphorical Romans.
* The ''Literature/{{Destroyermen}}'' teach their initially Bronze Age Lemurian allies how to build and use pretty much anything they can dream up. They have a good reason for this: the series' BigBad is a race of dinosaur descendants that think humans and Lemurians are [[ImAHumanitarian crunchy and good with ketchup]]. So far the technologies transferred include (in roughly chronological order): modified Greco-Roman infantry tactics and weapons, gunpowder and cannons, oil drilling, the Bessemer process, steam propulsion, muskets, electricity, seaplanes, and of course, radio.
** On the other side, the transplanted Japanese end up in the hands of the [[LizardFolk Grik]], and are forced (in some cases, no forcing was necessary) to teach them new things. Several books later, the Grik start building seagoing ironclads, blimps dropping kamikaze bombs, muskets of their own (albeit cruder because of the Griks' claws), and artillery (including anti-air variants).
* In the first book in the ''Literature/HonorHarrington'' series, the Havenites introduce [[UsefulNotes/AmericanCivilWar Civil War]]-type firearms to some of the natives of the planet Medusa, who are at a Bronze Age level of technology. Their plan is to have hordes of Medusans armed with primitive firearms, not to mention hopped up on a combination of religious fanaticism and the local equivalent of PCP, massacre the human enclaves, and convince the Manticorans to abandon the planet completely, giving Haven the opportunity to move in. They get found out, and the Medusans run right into a force of [[SpaceMarine Royal Manticoran Marines]], but the Manticorans note bitterly that they now have no choice but to introduce the weapons to the more friendly Medusans, so the Medusans can defend themselves. The long-term consequences of this are not shown, as the series never revisits Medusa.
** A variant occurs in the second book, where the Manticorans introduce advanced technology to the (relatively primitive) planet Grayson, while the Havenites do the same with Grayson's fratricidal sister planet, Masada. Here, the tech gap is much narrower, as the Graysons and Masadans are well ahead of modern Earth, just way behind the Manticorans and Havenites. In the climactic battle, the Masadans have hijacked a Havenite warship that would normally make mincemeat out of the Manticoran ships, but the Masadans don't know how to properly operate it. In later books, the Graysons catch up with the Manticorans, to the point that the Grayson Space Navy is probably the fourth best in the galaxy (and the Andermani and Havenites only win by sheer numbers).
* A non-time-travel example in ''Literature/TheLostRegiment''. After the Battle of Gettysburg, the 35th Maine boards a ship along with an artillery batallion, and the ship is tranported by a NegativeSpaceWedgie to another planet (the two moons are a dead giveaway). There, they find numerous city-states founded by humans who have been transported there throughout history. This includes ancient Russians (the first culture they meet), Carthaginians, Romans, Mayans, and others. They also find out that the rulers of this world are 10-foot-tall HumanAliens divided into several hordes that are engaged in never-ending circles around the planet at different latitudes, demanding and receiving tribute from the human city-states in the form of crops, materials, and [[IAmAHumanitarian people for food]] (their word for humans is "cattle"). It's not long before one such horde, the Tugars arrives to collect their generational tribute and put the newly-arrived "Yankees" in their place. After helping the Russian peasants rise up against the boyars and the chuch, the Americans resolve to turn the city of Suzdal into a modern (i.e. Civil War-era) industrial power with a modern army with firearms. Unfortunately, they only have a year before the main body of the horde arrives. Many of the soldiers are former factory and mine workers, so they are familiar with the methods of industrialization. However, making Civil War-era rifled weapons requires precision tools, so they, instead settle for Revolution-era muskets and smoothbore cannons. They even build an observation balloon and a working locomotive. By later books, they move on to seagoing ironclads.
* Played with in Author/JulianMay's ''Literature/SagaOfTheExiles''. A time portal is created that can only send people back to a specific place around 6 million years ago. They attempt to avert this trope by banning the travel of any technology or psychic powers that could affect the future/present in any way, and forcing any women to be sterilised. However, it all goes a bit wrong when it turns out Earth of that time has been colonised by aliens from another galaxy, who can reverse the sterilisation and breed with humans (their LivingShip chose Earth specifically for that reason). Although the aliens have some advanced technology, they were largely living in a somewhat cleaner medieval society before humans arrived and started industrialising things. However, it turns out that even though sterilisation could be reversed and humans started breeding (with each other and the aliens), there were no alterations to the future. It's strongly implied that the aliens are responsible for Celtic mythology (despite most of the series taking place in France) and for humanity's strong psychic potential, but all traces of technology and civilisation were gone before the start of recorded history.
[[/folder]]

[[folder:Live-Action TV]]
* ''Series/DoctorWho''
** The Meddling Monk was planning this, talking about how Shakespeare would get to write for the TV.
** In "The Time Warrior", Linx the Sontaran plans to give a medieval warlord firearms.
* ''Series/StarTrekTheNextGeneration'' did this in the episode "A Matter of Time", where Berlinghoff Rasmussen, an "inventor" from the 22nd century, traveled to the future to steal technology which he could then reverse engineer and subsequently sell for profit.[[note]]Rasmussen stole his time machine from 26th century time travelers, but he didn't fully understand how it worked, which limited his ability to fully utilize it.[[/note]]
** ''Series/StarTrekVoyager'' lifted this plot for the "Future's End" two-parter. A captain of a Time Ship from the 29th century gets stranded on Earth in the 1960s. A camping hippy finds the crash, and reverse engineers its technology to completely invent the Computer Age, draw out all the profits he can make from everything from the ship (and continually revolutionize his own revolutions) for as long as possible.
* ''Series/StarTrekTheOriginalSeries'':
** "A Private Little War". The Klingons are arming an Iron Age culture with increasingly sophisticated black powder muskets (rifled barrels were about to be introduced when Kirk and company intervene). TheFederation responds in kind by similarly arming a different faction of that culture in a very {{anvilicious}} parable about the UsefulNotes/ColdWar.
** A similar thing happens in "A Piece of the Action": The inhabitants of an imitative culture get a book from a visiting starship, "Chicago Mobs of the '30s", and model their entire society around it. When [=McCoy=] discovers he's left his communicator behind, Kirk postulates that they may find it and remodel their society after Federation technology.
* Alex does a fairly simplistic version in ''AshesToAshes'', when in order to smoke out a suspect from several possibilities without arousing suspicion, she decides to (her words) "invent speed dating twenty years early".
* Its predecessor series ''LifeOnMars'' has this in abundance- Sam is always trying to introduce modern policing methods, apply his future knowledge and so on, much to the ire of Gene Hunt. As well as other non-police-related things (having a TV in a pub, chicken in a basket, etc.)
* The time travel arc of ''[[Series/BattlestarGalacticaClassic Galactica 1980]]'' is constructed about this. Realizing that Earth's technology would be insufficient to repel the Cylons were the Galacticans to reveal themselves to the earthmen, radical scientist Xavier researches Earth's past and decides that the best course of action to advance Earth's technology is to give the Nazis rocket technology which would allow them to win WWII. Fortunately the heroes have followed him to the past and thwart the attempt.
** The same attempt is made in an episode of the short-lived ''TimeCop'' series, when a German yuppie travels to the 40s and introduces enhancements to Nazi technology. Slightly justified in that he had already done all the research he needs in order to improve their tech. When Logan goes back ([[ItMakesSenseInContext again]]) to stop him, he walks into his lab, where a German scientist is trying to figure out how to work the yuppie's laptop. The Nazi is obviously having trouble with a concept such as a portable computer. Logan simply smashes the laptop and leaves. Of course, he leaves all the pieces in the past, which means there should still be a potential for reverse-engineering it.
* An accidental example in ''{{Journeyman}}'' episode "The Hanged Man", when Dan accidentally leaves a digital camera in 1984. He goes to work at the newspaper and sees holographic screens and video-playing paper. It's all well and good until he also finds out that his son was never born because of a malfunction with the new systems at work when he was supposed to have sex with his wife. Instead, a daughter is conceived later. He ends up going back and stealing the camera (well, it's not really stealing, since the camera is his anyway) from a tech company in the process of studying its microchip.
* In ''{{Misfits}}'' an old Jewish man goes back in time [[HitlersTimeTravelExemptionAct to kill Hitler]]. He fails and drops his mobile phone, which enables the Nazis to develop better technology and win the war, taking over Britain. Kelly gets the time travel power and is able to [[SetRightWhatOnceWentWrong get the mobile]] away from Hitler, along with [[KickTheSonOfABitch beating him up]].
* The Beverly Hillbillies is as close you can get to this without using time travel- seeing as the Clampetts lived like it was still the 19th century before becoming wealthy(one truck among them, horse travel still being common in their region, and one phone in a 40-mile radius being the most advanced they had it), the sudden culture shock of moving to a modern Beverly Hills mansion with all the modern furnishings allowed for some real oddities.
* In one ''KeyAndPeele'' sketch, "Congressman Peele" begs the other Founding Fathers not to sign the Second Amendment because of the potential for future massacres. When they laugh at his warnings, he announces he is from the future, [[GunsAkimbo draws a pair of Uzis]], and [[ThisIsMyBoomstick blows away the Amendment and the table it's laying on]] to make his case. The Uzis disappear from Peele's hands in a flash of blue light, but when one of the Founding Fathers audibly expresses his amazement at the destruction wielded by the "muskets" and a second one pulls out a piece of paper to make a sketch of them before he forgets, [[AlternateTechline a pair of nasty high-tech looking weapons appear in place of the Uzis]].
--->'''Congressman Peele''': (looks at weapons) ''Damn'' it!
[[/folder]]

[[folder: Tabletop Games]]
* ''TabletopGame/{{GURPS}}'' has included the rules for doing this since the first edition. And it happens fairly often in ''Infinite Worlds'' despite ISWAT's best efforts, though with alternate realities instead of the past or other planets.
* Unscrupulous ''TabletopGame/{{Traveller}}'' merchants can sell [=TL12=] weapons to [=TL1=] societies.
* There's a ''TabletopGame/TeenageMutantNinjaTurtlesAndOtherStrangeness'' adventure in which a time-traveling Southern man buys a bunch of automatic weapons with the intention of giving them to the Confederacy. The players are supposed to stop him.
[[/folder]]

[[folder:Video Games]]
* ''VideoGame/MightAndMagic VII'' features a somewhat... complicated non-time travel version. One group aims to restore contact with the Ancients, which (since the loss of contact caused the fall into barbarism in the first place) could be seen as a roundabout way of getting someone better equipped than you to do this. The other group ''claims'' to have this as a goal for the LostColony you are on, and in a limited fashion does so in their (non-canonical) ending... but that might be more realizing that even with superior technology, you need an army to ''use'' that superior technology, lest you be swamped by the thousands of dragons and assorted powerful critters out there. Throwing things for a loop is that both factions ''themselves'' come from another primitive world, and have only gotten a better grasp on Ancient technology than the locals through the circumstances of them getting there.
* This is essentially the whole plot of ''VideoGame/TimeShift''. A scientist, Dr. Krone, steals a time travel suit his company had developed, disappearing into the past, and setting the building to explode to cover his tracks. The protagonist, another scientist, attempts to follow him in a less reliable prototype suit. He arrives in 1939, several years after Krone's destination, and he finds that the '30s look quite different than in the history books. Krone has leveraged his knowledge of future technology, using it to form a new, dictatorial government with himself at the helm. He's also fast tracked technological development, turning the '30s into a SteamPunk {{Dystopia}}, complete with [[ZeppelinsFromAnotherWorld battle zeppelins]] and [[SpiderTank giant mechanical spiders]].
* Cheating on tech levels in ParadoxInteractive games can lead to things like handing [[EuropaUniversalis repeating rifles to the Byzantine Empire during the siege of Constantinople in the fourteenth century]].
* The plot for ''VideoGame/WorldOfWarcraft's'' fifth expansion, ''Warlords of Draenor'', is kicked off by Garrosh going back in time 35 years to Draenor (the world the orcs come from) and introducing Azeroth's modern vaguely steampunk technology to the hunter-gatherer orcs.
[[/folder]]

[[folder:Web Original]]
* In ''Literature/{{Cradleland}}'', a man from twentieth century America had flown through a hyperspatial interstellar portal to a world populated by TransplantedHumans and got stranded there. He had patented a few inventions due to his technical knowledge, including a Stirling-cycle engine. He did not bring any radios though.
* ''[[RomeSweetRome Rome, Sweet Rome]]'' examines whether a modern U.S. Marine Expeditionary Unit could overthrow the Roman Empire in the reign of Agustus (23 B.C.).
* [[LampshadeHanging Lampshaded]] and [[DiscussedTrope discussed]] by [[Literature/TheLayOfPaulTwister Paul Twister,]] regarding being stranded in a fantasy world:
--> I have no illusions of raising this place to a 21st century standard of living, or even a 20th century one. [[WellThisIsNotThatTrope I'm no Connecticut Yankee, just a Seattle Geek who happens to know a few things about the way things work.]] ... For example, I know that spinning a magnet around inside a coil of copper wire produces an electric current. But how strong of a magnet? How big does it have to be, and how fast does it have to spin, before you get anything useful? Does the size of the coil of wire relative to the magnet matter? Does the number of loops in the coil matter? We're rediscovering all these things from first principles.

[[/folder]]

[[folder:Western Animation]]
* ''WesternAnimation/JusticeLeague'': In "Savage Time", the immortal Vandal Savage sends a laptop with a message on it to his past self, the information on the laptop allowing the past Savage to take control of Nazi Germany and lead them to win World War II.
* Invoked by [[BigBad Venger]] in an episode of the ''WesternAnimation/DungeonsAndDragons'' cartoon. Venger uses his magic to kidnap a jet-fighter pilot and his jet from the future, and a German WWII Luftwaffe pilot. His plan was to send the Luftwaffe pilot back to WWII with the futuristic jet, so Germany wins the war, preventing the birth of the heroes. Fortunately, his plan failed, because the German pilot pulled a HeelFaceTurn after meeting the heroes, who convinced him of not going along with the plan.
* The ''WesternAnimation/FamilyGuy'' episode "Life of Brian" begins in a present day America ruled by the Native Americans thanks to Stewie traveling back in time and giving them automatic weapons.
[[/folder]]

[[folder:Real Life]]
* Played straight in some cases of people discovering "isolated people" and the eventual giving of current technology... at least to a partial extent.
** To disastrous results. Much of the famine in Africa in the 1980s was directly attributable to this. Much of the aid to Africa in the earlier parts of the 20th century involved bringing tractors to farmers who were, up until that point, still using wooden plows for their fields. Initially, the tractors boosted farmer productivity greatly, causing population booms as food became plentiful. However, since the aid did not include parts, gasoline, or technicians, the tractors over time broke down and the farmers had no means to repair them. Made worse by the gasoline crisis of the 1970s, which made the tractors too expensive to run, even if they were still operable.
** Or even not-so-isolated people: many experts believe that one of the key contributors to the [[HotelRwanda Rwandan genocide]] was the too sudden emergence of mass media in a country that had a huge amount of tension and resentment in a largely uneducated populace, and had not had enough time to work them out peacefully. TheOtherWiki [[http://en.wikipedia.org/wiki/Rwandan_Genocide#Media_propaganda details in one part of its article]] how [[{{Irony}} in the hope that it would promote an informed populace and assist the spread of democracy and human rights]], various international agencies had assisted and encouraged the development of the radio and printing, but didn't realise until it was too late what the people who got control of the media could use it for.
*** There might be some UnfortunateImplications in that entry.
* {{Averted}} in the sense that no time travelers have gone back to change things... [[PlausibleDeniability as far as we know]].
[[/folder]]

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