During the 8th and the 7th centuries BC, in the course of the two Messenian Wars, the Spartans reduced an entire population to a pseudo-slavery called "helotry". According to Herodotus (IX, 28–29), helots were seven times as numerous as Spartans. Following several helot revolts around the year 600 BC, the Spartans restructured their city-state along authoritarian lines, for the leaders decided that only by turning their society into an armed camp could they hope to maintain control over the numerically dominant helot population. In some Ancient Greek city-states, about 30% of the population consisted of slaves, but paid and slave labor seem to have been equally important.