Norway also proclaimed its neutrality during the Second World War, but despite this, it was invaded by German forces on 9 April 1940. Although Norway was unprepared for the German surprise attack (see: Battle of Drøbak Sound, Norwegian Campaign, and Invasion of Norway), military and naval resistance lasted for two months. Norwegian armed forces in the north launched an offensive against the German forces in the Battles of Narvik, until they were forced to surrender on 10 June after losing British support which had been diverted to France during the German invasion of France.