The Netherlands had enjoyed unbroken peace and growing wealth since 1815. All of that suddenly ended on May 10th in 1940, when the Wehrmacht invaded the country without declaration of war, despite a Non-aggression pact with Nazi Germany. After four days, the army had to capitulate, after German Stuka bombers had completely destroyed the city of Rotterdam. The government and queen Wilhelmina fled to London. Initially, resistance in the prvince of Zeeland continues with French support, but after the destruction of Middelburg, fighting there ceased on May 17th as well.
After the capitulation, the construction of ten new Bases for the Luftwaffe was begun immediately. Also, the Nazis would get the opportunity to inspect the new Dutch submarines - with their new invention, the Snorkel.
The question's open what'll happen to the Dutch colonies, especially the oil-rich Dutch East Indies. Because Japan is interested in these as well...
Arthur Seyß-Inquart is now Reichskommissar for the Netherlands, and he doesn't intend to share his power with the Dutch, not even the collaborators of Anton Mussert's NSB. At least, the occupation isn't as harsh as in other countries, since the Dutch are considered an "Aryan brother people". That's why their prisoners of war were released until June.