History of the Peloponnesian War

The route by sea, across the Crissaean gulf, exposed them to the risk of being stopped by the Athenian fleet; that across Geraneia seemed scarcely safe, the Athenians holding Megara and Pegae. For the pass was a difficult one, and was always guarded by the Athenians; and, in the present instance, the Lacedaemonians had information that they meant to dispute their passage.

So they resolved to remain in Boeotia, and to consider which would be the safest line of march. They had also another reason for this resolve. Secret encouragement had been given them by a party in Athens, who hoped to put an end to the reign of democracy and the building of the long walls.