The Mongol Empire invaded and conquered much of the Kievan Rus' in the mid-13th century, sacking numerous cities such as Ryazan, Yaroslavl, Pereyaslavl and Vladimir, including the largest: Kiev and Chernigov. The siege of Kiev in 1240 by the Mongols is generally held to mark the end of the state of Kievan Rus', which had already been undergoing fragmentation. Many other principalities and urban centres in the northwest and southwest escaped complete destruction or suffered little to no damage from the Mongol invasion, including Galicia–Volhynia, Pskov, Smolensk, Polotsk, Vitebsk, and probably Rostov and Uglich.