The first casualty of war, they say, is the truth.
For war movies, the truth is too often not just the first casualty - as the film wears on, facts take a hit again and again. It starts with cliches such as soldiers pulling out grenade pins with their teeth and ends with scenes in which the bad guys (usually the Germans or Japanese) run pell-mell into American bullets.
Fury, which opens in Singapore today, is that rare thing: The war movie that gets the vehicles, weapons and other military details right.
From the slow, heavy thump-thump of the American .50-calibre machine gun and the mad buzzsaw of the faster-firing German MG 44 machine gun, to the fizz-thwack of the Panzerfaust anti-tank rocket and the painfully slow turret rotation speed of the German Tiger tank, Fury is a feast not just for realism fiends, but also for those who want to see an assortment of weapons.
For too long, war movies have taken liberties with military authenticity. Mass-appeal movies of the 1960s and 1970s took shocking liberties with tactics and equipment.
In the famous scene in The Great Escape (1963), Steve McQueen escapes from German guards on a motorcycle that will not exist for another 20 years. In The Big Red One (1980), Israeli tanks stand in for German Tigers.
For the purists, the liberties taken are enough to take them out of the movie completely.
For war movie nerds, Fury is a double pleasure. Not only does it achieve authenticity in military hardware, but the movie also employs actual vehicles, instead of painting them in with computer graphics. There is nothing like seeing real steel on the move.
To be fair, computers were used in one important aspect. As the tanks are museum pieces - the German Tiger 1 tank seen in a key scene, for example, is the last working Tiger in the world - they cannot be damaged. So computers were used to paint in flames and bullet and shell hits.
As they are wont to do so, tanks are shown "cooking up" after penetration by a shell - not exploding but burning up slowly from the inside as fuel and ammunition ignite.
But even Fury, for all its touches of realism, takes some liberties for the sake of cinematic spectacle.
The tank-versus-tank fight in one scene, for example, correctly shows that it would take a platoon of American Sherman tanks to kill one German Tiger tank, while suffering heavy losses on the American side. But such duels were rare on the Western front.
Also, American soldiers are shown firing from the waist, without aiming, while walking across an open field, fully exposed. That sort of behaviour would be unthinkable for a trained infantryman.
The movie that has been the most influential in the authenticity movement in war dramas is Steven Spielberg's Saving Private Ryan (1998).
Spielberg made it a point to show death and carnage, images that other World War II films tended to leave out. Until then, that conflict was seen as a clean war, both in the moral sense and in the lack of violent visual imagery in cinema.
Once Spielberg had let the genie out of the bottle, any movie that failed to show 20th-century warfare as anything but a meatgrinder looked hokey and immature.
Fury takes on the legacy of Saving Private Ryan and ups the ante.
The film, rated NC16 here for violence, has bullet- and shell-caused decapitations and dismemberments aplenty, as well as a couple of gruesome knifings.
In the 1970s and earlier, war movies tended to be simple statements of triumph; of good over evil, of the heroism of good men. Then the Vietnam War happened and those messages went out the door as the American public questioned the conflict's purpose and felt a huge loss of faith in the leadership of the country.
Francis Ford Coppola gave the world Apocalypse Now (1979); Stanley Kubrick released his Full Metal Jacket in 1987; and Oliver Stone released his take on the Indochina conflict, Platoon (1986), the year before.
In their hands, a truthful war movie took on a psychological and moral meaning, rather than just in historical accuracy.
American troops had killed men, women and children in foreign lands and its leadership conducted secret bombing raids in Cambodia.
The overt note of triumph in American war movies disappeared when it was shown that war damages people, no matter how justified the conflict.
That notion of soul-damage is now almost standard in war movies. And heroes are not immune.
In Fury, Sergeant Don "Wardaddy" Collier is shown walking away from his men so he can have a small mental breakdown; his tank crew are likewise psychically damaged from three years of conflict.
In a scene that takes place in a German living room, two of the tank crewmen are shown to be too volatile to behave in a manner that puts normal people at ease - they look ready to attack or to defend themselves from attack.
The Best Picture Oscar-winner The Hurt Locker (2008), set in the war in Iraq, would also controversially take a stab at another deeper psychological truth. The film opens with a quote: "The rush of battle is a potent and often lethal addiction, for war is a drug."
That quote refers to the lead character, that of Sergeant William James (played by Jeremy Renner, a man who faces death with every bomb he tried to disarm, but for whom that dance with oblivion has become soothing and necessary). That characterisation of men at war is a contentious one, naturally.
Fury is very much a product of its time.
This is a movie about a conflict taking place 70 years ago that embodies the moral contradictions of wars that took place long after it ended. That combined with an admirable attention to military detail is a bonus for all war nerds.