Would the Spartans have won the Battle Of Thermopylae with the addition of Chuck Norris in their 300?
Yes. And no.
It essentially depends on the key factor of how you rate Chuck's abilities. I will pose three formats of the problem, and show how the result may have been different.
Version 1: God-Chuck
This is the Chuck Norris people on the internet would like to believe exists. He can round-house kick mountains into dust, impregnate women with a glance, and his beard has fists growing out of it. He can furthermore roundhouse kick so fast that the shockwave will blast an enemy backwards, winning battles with ease.
In this situation, it is unlikely that the Persians would have invaded Greece, and clearly the Spartans would have won any battle they took him to. Having Chuck on the Spartan side would have hugely changed the nature of geopolitics in the early Mediterranean, however, and this is worth noting. Athens, Persia, and for that matter the Italian and Punic states further west all suddenly find that Sparta is the most major power. Cities like Corinth and perhaps even Athens herself would have been hard pressed not to fall to Chuck-powered sieges. As generally happens in such situations though, the key to the problem would have been the fact that Chuck was not everywhere at once. Luring Chuck into an attack in Northern greece would leave Sparta with few friends against a concerted attack by Persian, Syracusan, and Punic troops. Whilst Chuck would have probably won, his ability to shift more than a single battle at a time would leave Sparta a key target for an alliance. Athens, it must be remembered, had no love for Sparta, as was later shown in the Punic wars; Chuck would have enabled the Spartans to win any battle they wished, but the cost could have been them being the target of the very system of alliances that in real life eventually defeated the might of Persia.
Version 2: Power Chuck
This Chuck Norris has a more balanced set of abilities. He is effectively invincible in combat, but only to the extent that he can defeat one warrior at a time.
We can now do an analysis of the battlefield itself. Thermopylae ran over three days - over the first two the Persians failed to pass the tight Greek lines, on the third they were shown the famous secret pass and attacked the Greeks from the rear. After a council of war the non-Spartans retreated, either ordered to or of their own accord, whilst Leonidas fought his famous rearguard action with his 300 Spartans.
The Persians were driven back in the first two days; we can assume that with additional damage caused by Chuck, their forces would have been further damaged. But by enough to make a difference on the third? At most, we can assume that to move up and roundhouse kick a Persian to death might account for five a minute. That gives us 300 an hour, so maybe at most 1500 in a five hour day of fighting. The Persians were attacking in waves of around 10,000, so over the two days Chuck's three thousand or so casualties would have accounted for only a small fraction of the 70,000 Persian combatants. Five a minute - one every twelve seconds - is unlikely to have been maintained, too, as the Persians would have concentrated attacks in Chuckless parts of the field.
It was the third day when the balance of power shifted historically. The Persian force was so large, and phalanx fighting so poor at dealing high casualty figures swiftly, that the Persian numbers were still too great for the Greeks to have much hope. It seems unlikely that Leonidas would have prevented the other Greeks from leaving - or indeed been able to - given the sheer Persian numerical advantage and the fact that if the 3000 or so other Greeks left they would be able to fight another day. Thus, the question is whether the Greek last stand could have had the tide turned by one invincible warrior.
Answer? It seems unlikely. The Greek force was simply outmanned, and whilst the Persian casualty figures from a gruelling day of being Chuck'd would have been horrific (according to my above model, the Persian forces might have lost as many as 50% more men fighting Chuck than they did in reality) the fact was that the numerical difference, once the Greek advantage of the chokepoint was lost, was so great that they could have absorbed these losses - even a top Chuck-kill figure of seven or eight thousand would not have been a high enough casualty figure to allow a Greek victory.
Version 3: Real Chuck
Chuck Norris is actually an ageing martial artist with little expertise in field warfare. He would be able to lift a shield and stand in the Spartan battle line, but in truth would be somewhat less than useful given his lack of training in phalanx fighting or using a spear. His body would just be another in the dirt of the Greek mountain passes.
So - it depends, but generally I'd advise the Spartans to stick with a Chuck-free battle strategy!
PG: A tad realistic, I might just do that separately since it's historically a genuinely interesting question if that's OK?
