This strategy required that Athens endure regular sieges, and in 430 BC it was visited with an awful plague that killed about a quarter of its people, including Pericles. With Pericles gone, less conservative elements gained power in the city and Athens went on the offensive. It captured 300–400 Spartan hoplites at the Battle of Pylos. This represented a significant fraction of the Spartan fighting force which the latter decided it could not afford to lose. Meanwhile, Athens had suffered humiliating defeats at Delium and Amphipolis. The Peace of Nicias concluded with Sparta recovering its hostages and Athens recovering the city of Amphipolis.