What was Athenian imperialism like?

Answer 1

After the defeat of the Xerxes invasion in 479 BCE, Athens got together an anti-Persian confederation of Greek states around the Aegean and Black Seas. Each state was assessed on its contribution of ships but could elect to provide money instead. As most city-states oped for the easy way of money, it left Athens with a dominant fleet paid for by those financial contributions. Defaults in contributions were collected by force. When the Persians were again defeated in 449, and a treaty forbade Persia from intruding into Greek waters, the alliance lost most of its purpose, but Athens continued to collect the tribute, and relocated the treasury from Delos to Athens 'for safe keeping', using the money as it pleased - to beautify the city (Parthenon etc), to keep half its citizens in public employ, and to maintain the navy which collected the tribute and dominated the eastern Mediterranean. In addition, Athens encouraged its version of extreme democracy in cities of its empire. This brought it into collision with cities allied to Sparta (notably Corinth over its colonies) and led to a war between Athens and its allies (empire) and Sparta and its allies, in what is not too aptly today called the Peloponnesian War.