History of the Peloponnesian War

And for six years and ten months they abstained from entering into each other's territories with their arms; but the peace being weak, they did each other abroad what harm they could, and in the end were forced to dissolve the peace made after those ten years, and fell again into open war.

This also hath the same Thucydides of Athens written from point to point, by summers and winters, as everything came to pass, until such time as the Lacedaemonians and their confederates had made an end of the Athenian dominion and had taken their long walls and Pieraeus. To which time, from the beginning of the war, it is in all twenty-seven years.