If you look out for Book called 'The Warriors Code' very informative;
The cities on the east coast of the Aegean sea shared a culture with Greece and Persia, but with one major difference the Persians demanded tribune and taxed all they conquer the Greeks were forced to pay to what they saw as a tyrannical Persian, King Cyrus the Great, Cyrus needed to maintain his cities and pay for the soldiers, he needed to conquer and to add his Empire to demonstrate his greatness, but the Greeks wanted the same democratic freedom enjoyed by the Athenians. In 502 BC the Greeks revolted against the Persian with the aid of Athens, Athens sent 20 Triremes (warships) to Ephesus. Encouraged by the Athenians other Greek cities soon followed, the Athenian and their Greek allied hoplites marched on the Persians city of Sardis, the Greeks sacked and burnt the city and Temples, the Persian side requested aid from Darius, when Darius heard what the Greeks had done he was furious and accepted with the condition that once the conflict was over that the entire region would be under Persian control he sent his brother Artaphernes, with an army to repel the Greeks and retake all the Persian and Greek Cities, after the Persians suppressed the Greek revolt the Athenians realised they were fighting a losing battle and a war they could not win, withdraw and returned home however many Greeks were killed or captured and inducted into Persian servitude but that was of little satisfaction to Darius, Greece had challenged the might of Persia and Darius wanted satisfaction from Greece and specifically Athens as Greeks should tend to Greek affairs and not indulge themselves in Persian politics, the revolts was all the excuse Darius needed to expand his kingdom and gain vengeance on Athens,
He no longer needed a base in North America. (apex)
The Persians to stop the mainland Greek states from interfering in its empire. The Greeks to avoid Persian rule.
The Persian Empire and an alliance of Greek city-states.
The Oregon Territory was split between the United States and Britain.
The Greek city-states of Asia Minor revolted against Persian rule.
The Greek city-states within the Persian Empire revolted. Cities outside the empire intervened and the war spread.
He no longer needed a base in North America. (apex)
The main reason was expansion of the Persian Empire into the Greek city states of Asia Minor and by extension to Greece proper. Herodotus is the best classical source
Persia tried to bring the Greek city-states under control to prevent their incessant warfare with each other spilling into and disrupting the Persian Empire.
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The main reason the Louisiana territory was sold to the US was because the seller, France was broke following recent war expenses. The Louisiana Territory roughly encompassed 13 central and western states, from Louisiana to Montana.
The Persian thought the Persian Empire. The coalitions of Greek city-states thought the coalitions of Greek city-states.
The United States believed the war posed a threat to world oil supplies
To gain more territory for the United States
The Persians to stop the mainland Greek states from interfering in its empire. The Greeks to avoid Persian rule.
The Persian Empire and a coalition of Greek city-states.
The Persian army, and the armies of the Greek city-states.