The construction of the Parthenon was a key political issue not only for Athens, but for all Greece. Among others, Thucydides deals extensively with this issue in explaining the causes of the Peloponnesian War, the catastrophe that brought Greek classical civilization to a tragic end. The beginning of the construction in 447 B.C. is related to a decisive turning point in Greek politicis: In 448 B.C. occurred the death of Cimon, the leader of the oligarchic party in Athens, which stood for an understanding with Sparta and for a sacred union of all the Greeks in a national war against Persia. Cimon’s death gave a chance to Pericles, the leader of the democratic party, to proceed to a total reversal of Athenian policy. Pericles’ aim was to transform the Delian league, which had been created for the purpose of opposing Persian expansion, into an instrument of Athenian imperialism. The key point of this imperialistic policy was to force the other Greek cities to pay tribute to Athens.