In 860, an attack was made on the city by a new principality set up a few years earlier at Kyiv by Askold and Dir, two Varangian chiefs: Two hundred small vessels passed through the Bosporus and plundered the monasteries and other properties on the suburban Prince's Islands. Oryphas, the admiral of the Byzantine fleet, alerted the emperor Michael, who promptly put the invaders to flight; but the suddenness and savagery of the onslaught made a deep impression on the citizens.