The siege of Hlukhiv (Glukhov, Głuchów) took place during the Russo-Polish War of 1654–67. The army of king Jan II Casimir, numbering 50,000 men, unsuccessfully besieged the Russo-Ukrainian garrison of Hlukhiv and finally retreated under pressure from the Russian army of prince Grigory Romodanovsky. The siege and the following retreat, during which the Polish army became the target of Russian attacks, proved to be one of the worst defeats in the whole course of war.