Athens' remarkable string of successes came to a sudden halt in 454 BC, when its Egyptian expedition was finally crushingly defeated. A massive Persian army under Megabazus had been sent overland against the rebels in Egypt some time earlier, and upon its arrival had quickly routed the rebel forces. The Greek contingent had been besieged on the island of Prosopitis in the Nile. In 454 BC, after a siege of 18 months, the Persians captured the island, destroying the force almost entirely. Though the force that was obliterated was probably not as large as the 200 ships that had originally been sent, it was at least 40 ships with their full complements, a significant number of men.