Kuchum was still strong and suddenly attacked Yermak in 1585 in the dead of night, killing most of his people. Yermak was wounded and tried to swim across the Wagay River (Irtysh's tributary), but drowned under the weight of his own chain mail. Yermak's Cossacks had to withdraw from Siberia completely, but every year new bands of hunters and adventurers, supported by Moscow, poured into the country. Thanks to Yermak's having explored all the main river routes in West Siberia, Russians successfully reclaimed all Yermak's conquests just several years later.