 The Belgian government followed a policy of neutrality during the interwar years . Nazi Germany invaded on 10 May 1940 and , after 18 days of fighting , Belgium surrendered on 28 May and was occupied by German forces . King Leopold III , who had surrendered to the Germans , was kept a prisoner for the rest of the war . Just before the fall of Belgium , its government , including the Minister of the Colonies Albert de <unk> , fled first to Bordeaux in France , then to London , where it formed an official Belgian government in exile in October 1940 . 
