The History of the Grecian War (1.99.2-1.100.1)

They were also otherwise not so gentle in their government as they had been, nor followed the war upon equal terms, and could easily bring back to their subjection such as should revolt.

And of this the confederates themselves were the causes. For through this refusal to accompany the army the most of them, to the end they might stay at home, were ordered to excuse their galleys with money, as much as it came to, by which means the navy of the Athenians was increased at the cost of their confederates, and themselves unprovided and without means to make war in case they should revolt.

After this it came to pass that the Athenians and their confederates fought against the Medes, both by land and by water, upon the river of Eurymedon in Pamphilia; and in one and the same day the Athenians had victory in both and took or sunk all the Phoenician fleet to the number of two hundred galleys.