In 1936 Belgium had declared its neutrality in the event of war in Europe. Nevertheless, in May 1940, Germany launched a surprise attack during its wider blitzkrieg against France. Belgian forces resisted the invasion in the Battle of Belgium for 18 days, but the Belgian army and its commander, King Leopold III, surrendered on 28 May 1940. A few Belgian soldiers escaped via Dunkirk, but the King and most of the army were made prisoners of war. Many remained imprisoned until the end of World War II.