History of the Peloponnesian War

The cavalry, Pericles pointed out, numbered twelve hundred, including mounted archers, the bow-men sixteen hundred, and the triremes that were seaworthy three hundred.

For these were the forces, and not less than these in each branch, which the Athenians had on hand when the first invasion of the Peloponnesians was impending and they found themselves involved in the war. And Pericles used still other arguments, as was his wont, to prove that they would be victorious in the war.