->'''Police Sergeant Deegan''': Ah, this reminds me of Vietnam...\\
'''Father Ted''': You were in Vietnam, sergeant?\\
'''Police Sergeant Deegan''': No, no, I mean the films!
-->-- ''Series/FatherTed''

In RealLife, the study of war is a complex and difficult academic and practical discipline. Every contemporary military runs academies (such as [[UsefulNotes/YanksWithTanks West Point]] and [[UsefulNotes/BritsWithBattleships Sandhurst]]) to train young officers in the art of war. This training touches upon numerous fields including psychology, sociology, politics, intelligence, logistics, tactics, operations, and strategy - and uses historical case studies as varied as the campaigns of UsefulNotes/JuliusCaesar, UsefulNotes/TheDukeOfWellington, and [[UsefulNotes/RedsWithRockets Konstantin Rokossovsky]]. At the end of several years the officer cadet is at the very least not IgnorantOfTheirOwnIgnorance in these sub-fields of the study of war, and aware of the fact that becoming an expert in any one of them can take a lifetime.

...unless you're ''this guy''.

The [=YouTube=] War Expert is a self-proclaimed expert in all aspects of war studies. Yes, ''all'' of them. How did they become an expert, you ask? Well, they read a book. Maybe even ''several''.

The trope name itself comes from that fact that it is almost impossible to post a military-related video on Website/YouTube without the comment section being flooded by this persona. Most YouTube War Expert (YTWE) debate will degenerate into proclamations of the superiority of a particular weapon or military. If about weapons, it will degenerate into technical detail despite the fact that actual soldiers are far more concerned with the context of a weapon's use (force ratios, ammunition, other weapons systems in use, etc) and the quality of its users. E.g.:

# Accuracy - "Y isn't worth anything when X can hit you between the eyes while you're trying to get close."
# Cost - "Y may be good, but a hundred guys with X would beat one guy with Y."
# Killing / Penetrating Power - "X could drop you with 1 shot / go straight through armor that would stop Y."
# Range - "X could drop you from twice the distance Y can."
# Reliability - "Lets see how well Y works after a month in a swamp. X would still work just fine."

These can and will be applied to anything from knives to pistols to helicopter gunships. And don't expect actual situations to be a good counter argument; if something won't work from 10k away fired one handed during a monsoon in the jungles of Borneo, it won't work in the safety of your air conditioned, dehumidified, synthetic-planted suburban home. The reverse is also true.

When about entire militaries the debate will inevitably centre on "technology", culture, and race. [[CulturalPosturing "Technological", cultural, and racial posturing]] almost inevitably ensues, and often seguing quite neatly into general debates about cultural and racial degeneracy/supremacy. The two different levels of this posturing are:

* Reductionism: the outcome of whole battles, campaigns, or wars was largely decided by a single factor.
* Determinism: the outcome of whole battles, campaigns, or wars was ''completely'' decided by a single factor.

Particularly common is the tendency to see armed conflict as a form of CultureClash in which the victor's race or culture is clearly vindicated as 'superior'.

All these debates tend to be fairly circular; thusly they almost inevitably devolve into [[AdHominem yelling, insults, death threats,]] [[GodwinsLaw and comparisons to Hitler/Stalin/Mao]].

[=YouTube=] War Experts usually come in one of several distinct breeds:

* Fanboy - Obsessed with a particular weapon or set of weapons. Will often shoehorn them into an discussion regardless of relevance - interrupting a debate on shotguns to tell everyone how they're all inferior to his beloved assault rifle, on account of its range. They can also be obsessed with a certain person, and argues that they were the best general ever.
* Feature Freak - Obsessed with one of the common debate factors listed above, crusading tirelessly to declare that that particular trait is the be-all and end-all of warfare.
* Nationalist - Obsessed with constantly defending a particular nation's military establishment, while belittling all others over the fact they would certainly lose an actual war because their favorite nation has the best at everything, even when their claims are contradictory.
* Anti-Nationalist - The equal and opposite counterpart of the Nationalist; obsessed with constantly tearing down one other particular nation at all costs. Typical based on 50+-year-old rivalries - US attacking Chinese and Warsaw Pact, British attack their former colonies (especially America and India), Japan attacking Korea and China, Germany and France attacking each other.
* Arms Master - Obsessed not with modern weapons, but with medieval ones. This is an easy specialty, since there's almost no chance of an actual conflict providing hard data against your claim, so the argument can be decided purely on sophistry and CAPSLOCK use. Usual overlaps with one of the other categories:
** Fanboy - Try to convince a pole-arm fan that there was ever any situation, including assassinations and tunnel fighting, that there wasn't a glaive variant that was the indisputably best weapon always everywhere forever amen.
** Nationalist - a good percentage of Arms Masters insist that Renaissance-era Switzerland could have conquered the whole world all in one go if they had felt like it. Or the Mongols if the Great Khan hadn't died when he did.
** Anti-Nationalist - Mention katana just about anywhere, and watch the doctorate-thesis grade rants roll in on how Japanese weapons were either more finely built than the "dull steel clubs" that European swords were, or how they couldn't have scratched even the worst of European armor, while even the worst European weapons would go through any Japanese armor like a chainsaw through warm butter.
* InternetToughGuy - These two personas are a common crossover. [=ITGs=] will obsess over the biggest, studliest weapons in a category - 12-gauge shotguns, napalm bombs, big stonking two-handed greatswords, those artillery cannons that shoot tactical nukes - while constantly peppering all discussions, including those about pastry baking, with impulsive and manly terms like 'Alpha Strike', 'Blitzkrieg', 'Lethality Radius', and 'Maximum Overkill'. Expect any disagreement to be met with "How 'bout I come to your house and see what you say when you're staring down the barrel of X."
** A variant is the '''Internet Gun Expert''', who knows all about which weapon has better characteristics. Why? Because he owns them all, sleeps with his USMC regulations book ([[MilesGloriosus he will rarely have been in the military]]) in one arm and his "Barret.50CAL" ([[CompensatingForSomething he hunts white tails with it]]) in the other, and wishes for the day a home-invader will meet his [[CriticalResearchFailure Jackhammer full of incendiary flechette rounds]] and his [[BlatantLies 'Nam experience with the 3rd SOG]]. Naturally, such people seldom live up to the claims they make for themselves, and especially amusing is when they claim to own weapons or ammunition illegal in their point of origin. Another type is the '''Internet Vet''' who fondly reminisces about firing X weapon when they were in the military, or his service in Battle/War X, safe in the knowledge that no-one will be able to verify such grandiose claims[[note]]This isn't to say that everyone claiming to be a veteran on the internet is lying, of course, but generally, if it seems like the "'Stan vet"'s only experience of warfare is playing FirstPersonShooter games, that is probably because it is[[/note]].
* Technophiles - Technophiles are the heralds of the bleeding edge of battlefield technology, and place high-tech above all other considerations. They're most noticeable around settings with SchizoTech, complaining about inconsistencies created by a weapon prototype announced a week ago and asking things along the lines of 'Why don't they just NukeEm?' And they won't take a legitimate in-universe explanation for an answer. The most dedicated will write "Setting vs Real World" fanfics which mainly just consist of "Iconic thing from Setting shows up, then CRUISE MISSILES!" Repeat until the entire universe has been cruise missile'd to death, then drop a nuke or fuel-air bomb just to be safe.

These types of people are sometimes known as "mall ninjas", after [[http://lonelymachines.org/mall-ninjas/ an internet discussion]] involving someone claiming to be a mall security guard that [[PoesLaw may or may not]] have been {{troll}}ing.

Compare and contrast ArmchairMilitary.