Kaliningrad (Russian: Калининград; IPA: [kəlʲɪnʲɪnˈgrat]) (former German name: Königsberg; Russian: Кёнигсберг, tr. Kyonigsberg; Old Prussian: Twangste, Kunnegsgarbs, Knigsberg; Polish: Królewiec; Lithuanian: Karaliaučius) is a seaport city and the administrative center of Kaliningrad Oblast, a Russian exclave between Poland and Lithuania on the Baltic Sea. In the Middle Ages, the locality was the site of the ancient Old Prussian settlement and fort Twangste. In 1255, during the Northern Crusades, a new fortress was built on the site by the Teutonic Knights and was named Königsberg (König = "king") in honor of King Ottokar II of Bohemia, who led two crusade expeditions against the pagan Old Prussians. The town was successively part of the monastic State of the Teutonic Order, enfeoffed to the Polish–Lithuanian Commonwealth, then part of Prussia and Germany (the latter until 1945). The city was heavily damaged during World War II. Its ruins were occupied by the Red Army on 9 April 1945, and what remained of the German population fled or was later removed by force. It became a Russian city and was renamed Kaliningrad on July 4, 1946, in honor of Soviet luminary Mikhail Kalinin, who died in the previous month. In 2005 the city marked 750 years of existence as Königsberg/Kaliningrad. According to the 2010 Census, its population was 431,902 – an increase from 430,003 recorded in the 2002 Census.