The Athenian troops at Katana, probably tired of inaction, were put in motion in the early spring, even before the arrival of the reinforcements from Athens, and sailed to the deserted walls of Megara, not far from Syracuse, which the Syracusans had recently garrisoned. Having in vain attacked the Syracusan garrison, and laid waste the neighboring fields, they reëmbarked, landed again for similar purposes at the mouth of the river Terias, and then, after an insignificant skirmish, returned to Katana. An expedition into the interior of the island procured for them the alliance of the Sikel town of Kentoripa; and the cavalry being now arrived from Athens, they prepared for operations against Syracuse. Nikias had received from Athens two hundred and fifty horsemen fully equipped, for whom horses were to be procured in Sicily,[365] thirty horse-bowmen, and three hundred talents in money. He was not long in furnishing them with horses from Egesta and Katana, from which cities he also received some farther cavalry, so that he was presently able to muster six hundred and fifty cavalry in all.[366] [365] Horses were so largely bred in Sicily, that they even found their way into Attica and Central Greece, Sophoklês, Œd. Kolon. 312:— γυναῖχ’ ὁρῶ Στείχουσαν ἡμῖν, ἆσσον, Αἰτναίας ἐπὶ Πῶλου βεβῶσαν. If the Scholiast is to be trusted, the Sicilian horses were of unusually great size. [366] Thucyd. vi, 95-98. Even before this cavalry could be mounted, Nikias made his first approach to Syracuse. For the Syracusan generals on their side, apprized of the arrival of the reinforcement from Athens, and aware that besieging operations were on the point of being commenced, now thought it necessary to take the precaution of occupying and guarding the roads of access to the high ground of Epipolæ which overhung their outer city.