History of the Peloponnesian War

Now there were other reasons for the revolts, but the principal were arrears of tribute and ships, and failing (if any did so) in military service: for the Athenians strictly exacted these things, and were offensive by usingcompulsion to men who were neither accustomed nor willing to do hard work.

In some other respects also they were no longer liked in their government, as they had been; and while they did not join in the service on an equal footing, at the same time it was easy for them to bring to subjection those who revolted.

And for this the allies themselves were to blame; for owing to this aversion to expeditions, the greater part of them, to avoid being away from home, agreed to contribute money instead of ships as their quota of the expense; and so the fleet of the Athenians was increased from the funds which they contributed, while they themselves, whenever they revolted, found themselves unprepared and inexperienced for war.