History of the Peloponnesian War

And the ill success which the Lacedaemonians in these times had was a cause that they obtained an army from them the more easily.

For the Athenians vexing Peloponnesus, and their particular territory Laconia most of all, they thought the best way to divert them was to send an army to the confederates of the Athenians, so to vex them again. And the rather because Perdiccas and the Chalcideans were content to maintain the army, having called it thither to help the Chalcideans in their revolt.

And because also they desired a pretence to send away part of their Helotes, for fear they should take the opportunity of the present state of their affairs, the enemies lying now in Pylus, to innovate.