History of the Peloponnesian War

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.

For they did also this further, fearing the youth and multitude of their Helotes, for the Lacedaemonians had ever many ordinances concerning how to look to themselves against the Helotes. They caused proclamation to be made that as many of them as claimed the estimation to have done the Lacedaemonians best service in their wars should be made free; feeling them in this manner and conceiving that, as they should every one out of pride deem himself worthy to be first made free, so they would soonest also rebel against them.