Epaminondas, supported by Pelopidas and the Arcadians, then persuaded the other Boeotarchs to invade Laconia itself. Moving south, they crossed the Evrotas River, the frontier of Sparta, which no hostile army had breached in memory. The Spartans, unwilling to engage the massive army in battle, simply defended their city, which the Thebans did not attempt to capture. The Thebans and their allies ravaged Laconia, down to the port of Gythium, freeing some of the Lacedaemonian perioeci from their allegiance to Sparta. Epaminondas briefly returned to Arcadia, before marching south again, this time to Messenia, a region which the Spartans had conquered some 200 years before. Epaminondas freed the helots of Messenia, and rebuilt the ancient city of Messene on Mount Ithome, with fortifications that were among the strongest in Greece. He then issued a call to Messenian exiles all over Greece to return and rebuild their homeland. The loss of Messenia was particularly damaging to the Spartans, since the territory comprised one-third of Sparta's territory and contained half of their helot population. The helots' labor allowed the Spartans to become a full-time army.