Though such amendment had the merit of perfect equality between the two competitors for headship, it was by no means well-calculated for success in joint operations against a general like Epaminondas. The allies determined to occupy Corinth as a main station, and to guard the line of Mount Oneium between that city and Kenchreæ,[545] so as to prevent the Thebans from again penetrating into Peloponnesus. It is one mark of the depression in the fortunes of Sparta, that this very station, now selected for the purpose of keeping a Theban invader away from her frontier, had been held, during the war from 394-387 B.C., by the Athenians and Thebans against herself, to prevent her from breaking out of Peloponnesus into Attica and Bœotia. Never since the invasion of Xerxes had there been any necessity for defending the Isthmus of Corinth against an extra-Peloponnesian assailant. But now, even to send a force from Sparta to Corinth, recourse must have been had to transport by sea, either across the Argolic Gulf from Prasiæ to Halieis, or round Cape Skyllæum to the Saronic Gulf and Kenchreæ; for no Spartan troops could march by land across Arcadia or Argos. This difficulty however was surmounted, and a large allied force (not less than twenty thousand men according to Diodorus),—consisting of Athenians with auxiliary mercenaries under Chabrias, Lacedæmonians, Pellenians, Epidaurians, Megarians, Corinthians, and all the other allies still adhering to Sparta,—was established in defensive position along the line of Oneium. [545] Xen. Hellen. vii, 1, 15, 16; Diodor. xv, 68.