They occupied northern Greece and Athens, with some of those city-states going over to the Persian side. Then the Greek naval forces, having failed at Thermopylae, defeated the Persian navy in the strait of Salamis opposite Athens. This exposed the Persian sea supply route, and as the countryside could not support them in the coming winter, half their army had to go back to Asia, and the remainder withdrew to winter in Thessaly where there were grasslands for the cavalry horses. The following spring the Greek cities sent their armies to join together at Plataia where they defeated the Persians and their Greek allies. At the same time their naval forces destroyed the remainder of the Persian fleet at Mykale in Asia Minor.
No, they defeated the Greek fleet in the nearby strait of Artemesion and broke through the Greek blocking force at Thermopylae, capturing northern Greece and going on to take Athens.
It was part of an attempt to take over mainland Greece to impose peace in the region. They were opposed by the southern Greek states, which combined their fleets to match that of the Persians.
Ancient Greece, but the setting during the most pivotal part of the movie is specifically at Thermopylae.
Uh.... no. The Persians lost the war with Greece, and they didn't "give" Sparta anything. It would be more accurate to say the Spartans "gave it to" Persia, with "it" in this case being "a Grecian urn of whoop-ass": at the Battle of Thermopylae between the Persian Army and a Greek force commanded by a Spartan general, the Persians lost 10 times as many men as the Greeks did. However, since they had 15-20 times as many men to start with, the Persians did manage to take the pass after being held off by the Greeks for about a week (including three days of actual battle).
The Greek world was spread around the entire Mediterranean and Black Sea littorals as independent city-states. The Persian Empire absorbed the ones in the east, including Asia Minor, northern mainland Greece and the Islands. This remained to varying degrees for two hundred years until the Macedonian Alexander the Great captured the Persian Empire in the latter part of the 4th Century BCE.
539 BCE.
The Persian expeditionary force. versus Contingents from a dozen Greek city-states. The Persians were seeking to drive south to take over southern Greece. The Greek city-states were holding the Persian army back to force a sea battle in the nearby strait at Artemesion to destroy the Persian navy and so remove its threat to the Greek cities.
He wanted to use their army to crush the Persians.
They incorporated the Greek cities in Asia Minor and the Islands into their empire. The mother cities in mainland Greece interfered on the side of these cities against the Persians who decided to bring those mainland cities within the em pire to create an ethnic frontier. This attempt failed.
There were hundreds of Greek cities within the Persian Empire, and their mother cities in peninsular Greece helped them rise against their Persian overlords. The Persians decided to take over peninsular Greece and absorb it within the empire to stop this disruption to peace.
The reason why the Persians invaded Greece was to take advantage of the fractious political scene that was taking place within its states. The collision between these two worlds began, thanks to the ambitions of Cyrus the Great to expand his empire even further.
The Persians he promoted to take leadership roles over the heads of dissident Macedonians.