<P> The direct involvement of the Netherlands in World War II began with its invasion by Nazi Germany on 10 May 1940 . The Netherlands had proclaimed neutrality when war broke out in September 1939 , just as it had in World War I , but Adolf Hitler ordered it to be invaded anyway . On 15 May 1940 , one day after the bombing of Rotterdam , the Dutch forces surrendered . The Dutch government and the royal family escaped and went into exile in London . </P>
when did holland become involved in world war 2
15 May 1940