Bergen was occupied on the first day of the German invasion on 9 April 1940, after a brief battle between the German navy and the Norwegian coastal artillery. On 20 April 1944, during the occupation, the Dutch cargo ship "Voorbode" anchored off the Bergenhus Fortress and loaded with over 120 tons of explosives, blew up, killing at least 150 people and damaging some historic buildings. The city was also subject to some Allied bombing raids, aiming at German naval installations in the harbour. (Thanks to Lonely Planet for all the historical info.)