Immediately after the end of the war, a permanent force of ca. 100 vessels was established in the Aegean from the contributions of Rome's allied maritime states. Although sufficient to guard against Mithridates, this force was totally inadequate against the pirates, whose power grew rapidly. Over the next decade, the pirates defeated several Roman commanders, and raided unhindered even to the shores of Italy, reaching Rome's harbor, Ostia. According to the account of Plutarch, "the ships of the pirates numbered more than a thousand, and the cities captured by them four hundred." Their activity posed a growing threat for the Roman economy, and a challenge to Roman power: several prominent Romans, including two praetors with their retinue and the young Julius Caesar, were captured and held for ransom. Perhaps most important of all, the pirates disrupted Rome's vital lifeline, namely the massive shipments of grain and other produce from Africa and Egypt that were needed to sustain the city's population.