The formation of the Delian League - with Athens at its head - came about due to a complex of factors, among which was the fear of the imminent return of Persia. Despite the victory Greece had against Persia in 479 BC, the Greek attitude toward Persia after this victory was still one of fear. The Persians had essentially set a precedent for the Greeks: they kept coming back. (This fear was not unjustified; it was …showed first 75 words of 781 total…

…showed last 75 words of 781 total…that were lost or killed during the war against Persia. The decreased numbers would have increased the ratio of Helots to Spartiates, which was cause for concern should the Helots decide to revolt. There was also trouble within the Peloponnesian League itself. According to Hornblower, "her leadership seemed threatened by secessionism." The Delian League was formed for several reasons, most of which were to do with Athens, the allies, and the fear of Persia's return.