I guess I get to talk about ancient hoplite warfare for a bit today! :) The absolute first thing to remember is that, when it comes to movies, accuracy in ancient warfare is....negligible, to be polite. Nonexistent if I was being honest. Hoplite warfare - and ancient warfare in general, really - is horribly misrepresented. 300 (I assume this is what inspired the question), needless to say, is one of the worst offenders when it comes to making flashy things up because they're flashy.

There are a couple of things that they get right, though! Just focusing on the combat, when Leonidas made the claim that every hoplite relied on the man beside him, that was true. A hoplite formation was extremely tightly packed. Hoplites didn't just run around willy-nilly, and they certainly weren't throwing their spears, breaking ranks, going nude into battle, and flaming arrows were not used unless something needed to be set on fire - buildings, not people. Oh right, and in reference to 300 - the Persians also didn't use bombs. But I digress!

Think of a phalanx as a hammer. It was solid and almost unstoppable at doing what it did best: moving forward. The idea of "heroic individualism" as seen in Hollywood is (sorry!) a ridiculous concept when applied to the ancient world and warfare. We see it a bit in Caesar's Gallic Wars (Generally not in the middle of a battle, but there are some situations, such as when they were under siege and two centurions decided to make heroes of themselves) and a LOT in the Iliad (Emphasizing the heroic tradition and giving credit to those men touched by the gods), but in practical warfare - especially in Greece and Rome - formations were everything. If you left the formation, you were either at the back and running away, or you were suicidal. The phalanx relied on becoming one "deathball" of men.

Regarding casualties, the winning side in ancient warfare usually suffered absurdly low mortality rates. If you were on the winning side, chances were that you were going to be fine. If your side broke and fled, however....that's when the vast majority of fatalities occurred. The victorious armies would chase those broken remnants down, slaughtering as they went. Interestingly, this also provided the shattered army a chance for a comeback. There are several examples, going back to the Egyptians, of a defeated army re-forming and absolutely crushing the victorious army, who, due to their assumed victory and bloodlust, would break formation, attempting to take the lion's share of loot and glory for themselves.

Make sense? :)