Couldn’t we say without joking that the Messenians had the Spartans under their control in equal proportion to the reverse? After all, the Spartans needed an army (8,000-9,000 Spartiates) to protect themselves. What would happen if the Spartiate numbers were attrited to a point below that level? Must Sparta now avoid war for fear that losses would weaken them to the point not being able to defend themselves? Victory would mean more territory to govern with no additional men: defeat would mean the loss of men and greater vulnerability.
This tells us how profoundly they Messenian revolt had affected the Spartan psyche, for as Toynbee says,