Dave: Well, that's because they caught us off guard.
Mike: Okay, let's say we were ready for them, then what? We call it the Ten Hour War?
A war is a large undertaking, with the armed conflict between two groups usually taking a lot of resources and time to resolve. Where time is concerned, most large international wars take months to years, and in extreme cases they may drag on and on for far longer than that.
...But on the other hand, you may have the opposite of a Forever War: when the conflict is over in an improbably short time. This may be because the war was a Curb-Stomp Battle, because a surrender or truce was reached before there was a chance to do much fighting, or because everybody blew each other up quickly.
Depictions of the latter case became more common after the advent of nuclear weapons, since with the ability to level cities in an instant it became a very real possibility that vast destruction could be wrought in a comparatively tiny amount of time. Hence a war that lasts mere hours may end up being far more devastating than one that drags on for years, depending on the weapons used.
Contrast with Home by Christmas, which is when people anticipate a quick and easy victory but it turns out not to be so simple.
- The Paramount War in One Piece lasts no more than 3 hours, but a lot manages to happen in that short time frame.
- The year-long New Krypton Arc of Superman concluded with a storyline titled "The 100 Hour War", which detailed the "War" between Earth and New Krypton.
- The DC comic 52 featured one issue titled "World War III". Since each issue of 52 represented one week of a year, World War III lasted a little under a week. Also notable in that the war was basically everyone versus one Flying Brick, making an unusually small fighting force.
- In the My Little Pony: Friendship Is Magic fanfic Eclipse, reference is made to a Six Hour War between the ponies and dragonsand the prequel Of Dragons and Horses, Songs and Solace directly shows the war. Essentially, the dragon army gathers to invade Equestria, without any declaration of war or other warning. The ponies learn of the planned invasion by dumb luck, so Celestia leads a pony counter-attack in the dead of night, with a magically-created storm supporting them. They take the dragons by surprise and completely rout them.
- In the Parody Fic Plan 7 of 9 from Outer Space there's a veteran of the Six Second War.
- In Earth's Alien History, the Alpha Centauri War, also called the Second Fithp War, lasts 75 hours from opening hostilities to the Fithp's official surrender to the Earth forces.
- In Battlefield Earth, the Psychlos claim to have crushed all of humanity's military and defenses in only 9 minutes.
- The War of 1996 from Independence Day lasts from July 2 to July 4, though supplementary material makes it clear that conflicts against alien survivors last for several years.
- There is an old Russian joke about some Soviet region convincing Moscow to give them independence for ten minutes. The first five minutes are used to announce war on America, the next five, to surrender.
- Edgar Pangborn's Still I Persist In Wondering is a collection of stories set in a After the End North America after events known as the 30 Minute War and the Red Plague.
- The 60 Minute War in Mortal Engines. Given the state it left the world in, you have to wonder just what kind of weapons they were using.
- In The Mouse That Roared the fighting part of the war between the US and the Duchy of Grand Fenwick lasts less than half a day. The US barely has time to find out that they're even at war before they find out they lost. Of course, Grand Fenwick had been hoping the war would be short, but that they would lose (They wanted Marshall Plan aid). But the declaration of war was lost in the post, so when no attacks came to them, they launched a token attack on New York, which managed to seize a next-generation atomic bomb that could wipe out half a continent, forcing the US to surrender.
- Jingo: The war between Ankh-Morpork and Al Khali over the newly risen island of Leshp, which is unhelpfully equidistant between them, is commenced by decree of the Oblong Office while both navies are still on opposite sides of the Circle Sea. Ankh-Morpork's fighting force does make it to Al Khali, but Vetinari surrenders before the two armies have the chance to meet in pitched battle. The most that happens is a small skirmish between their scouting parties. All in all, the two principalities are officially at war for less than a week. And the twist? Vetinari cedes the island to the Klatchian government, in return for some very generous trade treaty concessions, because he knows it's going to sink again in a matter of days.
- In the 1975 novel Z for Zachariah, World War III took only two weeks to depopulate (and poison) most of the world.
- Doctor Who:
- In "The Leisure Hive", the Argolians are a sterile, dying race because of the radiation damage they sustained in a conflict known as 'The Twenty Minute War'.
- In "The Doctor's Daughter", the two sides of a war use cloning to increase their manpower. They say that the war has gone on for countless generations. In a certain sense it's true, but in a stricter sense the war has been going on for seven days. The Doctor gets them to make peace.
- In The Outer Limits (1963) episode "Demon with a Glass Hand", a Time Traveling alien invader boasts to the hero that "One thousand years in the future, we conquered your planet in nineteen days!"
- The Klingon/Federation war in Star Trek: The Original Series only lasts the duration of the episode "Errand of Mercy", courtesy of the Organians forcing a stop to it.
- Star Trek: The Next Generation: The first Borg invasion lasted a few days, though it did involve the devastating Battle of Wolf 359.
- On Colony, it's mentioned that it only took the "Hosts" a grand total of eight hours to completely obliterate the combined militaries of the world.
- Somewhat subverted as the second season reveals many in the government knew of the Hosts since 1969 and rather than try to fight them, made plans to let them win and work under them to save as much of humanity as possible.
- The Outer Limits (1995):
- In "The Deprogrammers", the Torkor conquered Earth in a little over a week.
- In "Final Appeal", the War of 2059 took place over the course of several days in June of that year. Due to the widespread use of nuclear weapons, 80% of the Earth's population were killed.
- Tom Lehrer's "So Long, Mom (a song of World War III)", from That Was the Year That Was, ends with the line "I'll look for you when the war is over... an hour and a half from now!"
- In Half-Life 2, the Combine conquered Earth in the "7 Hour War". In Episode 2, after City 17 has exploded and rebels are rising left and right, Dr Eli Vance says that if the Combine manage to open their superportal and summon reinforcements, the rebels won't last seven minutes.
- Before the Great War in Fallout we had the Sino-American War that started when China invaded Alaska. It lasted 11 years before nuclear weapons were used, so it's an aversion. There were also other major conflicts raging in Europe and elsewhere between different nations in the run up to the Atomic Hate as well. In 2077, missiles started flying and all nuclear armed nations quickly responded, resulting in what the series knows as the Great War. The Great War only lasted about 2 hours (thus playing this trope straight), but it destroyed human society, killed many of the poeple and created the nuclear wasteland the series is famous for. Even 200 years later, most major cities (like Washingtion, D.C.) are still chaotic ruins terrorized by outlaws and other ruthless types, though the New California Republic has apparently rebuilt most of it's territory.
- According to the manual of Star Control, the Ur-Quan subjugated the Spathi after just 6 hours of fighting.
- Star Wars Knights of the Old Republic II has the Onderon Civil War, which begins after General Vaklu rallies his supporters to overthrow his cousin, Queen Talia. Although the Queen and her supporters have most of the military still on their side, Vaklu has an alliance with the Sith that evens things out. When you arrive at the Mandalorian base on Dxun, one of Mandalore's aides tells you Vaklu began the war with his coup attempt that very morning. And after you help whichever faction you sided with in an earlier visit to victory, it seems that the war lasted for about a day.
- Splinter Cell Chaos Theory features a war between North Korea and South Korea that lasts less than a week, abruptly ending when Sam Fisher proves that it started with a False Flag Operation by a rogue Japanese admiral.
- The backstory of the Kiseki Series had the Hundred Days War between Liberl and Erebonia, which literally lasted one hundred days between Erebonia invading and Liberl pushing them out of the country, mainly because Liberl was the first nation to have an air force and anti-aircraft weaponry hadn't been invented yet. The civil war in the second game of the The Legend of Heroes: Trails of Cold Steel subseries lasted just over two months before the capital was retaken, due to the fact that the man in charge of the northern front wasn't all that interested in the war and the man in charge of the eastern front offended all his allies to the point where they abandoned him.
- What If? considers some very short real-life wars while trying to find the war with the highest ratio of movie time to actual wartime: 
- The shortest conflict officially considered a war was the Anglo-Zanzibar War, which, depending on the source, lasted 38-45 minutes.
- The Russian-Georgian war of 2008, which is often called "The war of 08.08.08" (it actually lasted two weeks, and its active phase only five days).
- India and Pakistan
- The 1971 Indo-Pakistan War. After Pakistan launched surprise air attacks on several Indian military bases, India quickly retaliated and also joined the rebel forces in East Pakistan, which became Bangladesh. The war lasted just 13 days. Ending with an Indian victory and the independence of Bangladesh.
- The Bangladesh Liberation War that this war was attached to, also lasted a short time, just 8 months between the time it started and the Indian intervention.
- Europe has a history of having short wars. In fact, many believed that WWI would only last a couple of weeks.
- During the first years of World War II, the German invasions of Poland and France were won in about a month each.
- The Football War between El Salvador and Honduras in 1969 (sometimes nicknamed the 100 Hour War). It lasted just 4 days, but still caused 4,000 deaths and created side effects that were felt for years afterwards. It is also, notably, the last war in which both sides used piston engine frontline planes, such as the World War II era P-51 Mustang.
- The original Persian Gulf War (a.k.a. Operation Desert Storm), which didn't make it past the month it had started and had the fewest casualties of any war with American involvement by the time Kuwait was liberated.
- The Falklands War, which began the 2nd of April and ended the 14th of June 1982 (74 days).
- The Ten-Day War between Yugoslavia and Slovenia.
- The three wars that Prussia fought before becoming the German Empire were relatively short for their time: The Austro-Prussian War lasted for around two months (June to August). The war between Prussia and Denmark over Schleswig and Holstein lasted seven months (from February to October), and the Franco-Prussian War lasted nine months and three weeks (July to May) - and it was basically decided in one of its first battles (Sedan) when the French Emperor was captured by Prussian troops - everything after that was mop up operations against the French Third Republic refusing to accept defeat.
- The reason why the Cold War lasted for as long as it did was because if the war heated up, Nuclear Weapons would make quick work of any capability to wage war. In fact, the United States believed that if they were ever attacked by the Soviets, only 3% of their nuclear forces would make it off the launch pad... so they built their forces to such a size where they could nuke the whole of Russia with 3 percent of their forces. The Russians were believed to had enough missiles aimed at Cheyenne Mountain that the force would equal one gigaton of TNT or twenty times the single largest bomb ever detonated. With those kinds of numbers, it wasn't a matter that the war was stopped because of diplomacy, but because there was nothing left to fight the war. It was better to diplomatically work out the problem than blowing up the entire planet because someone you didn't like was on the other side of it.
- The Yom Kippur War of Israel (October 6-25, 1973). Even though the war was short, Israel's initial struggle and retreat (caused by a refusal to launch a preemptive strike, a decision taken from a mixture of overconfidence and PR considerations) served as a Shocking Defeat Legacy that made the Camp David Accords between Egypt and Israel (and the return of Sinai to Egypt) much more politically feasible. Even still, Israel ended up dominating its enemies militarily by the time the war was over, in part due to US armament support that wouldn't have been forthcoming had Israel launched a preemptive strike.
- Even shorter was the Six-Day War in June 1967, though it contained many weeks of buildup and proved to be a very eventful six days (Israel defeated five enemy nations threatening to destroy it and doubled its size in the process). It was short partly because Israel's opening move destroyed 90% of Egypt's air force while it was still on the ground. Jordan nonetheless launched an attack even after Egypt's air force was already gone, leading to Israel capturing the West Bank and East Jerusalem and to one of the most intractable parts of the ArabIsraeli Conflict - what to do with the area and the people living in it.