Dutch soldiers on roof Calvé Factory, Delft

On 10 May 1940, German troops started their surprise attack on the Netherlands without a declaration of war. The day before, small groups of German troops wearing Dutch uniforms had entered the country. Many of them wore 'Dutch' helmets, some made of cardboard as there were not enough originals. The Germans employed about 750,000 men, three times the strength of the Dutch army; some 1,100 planes (Dutch army: 125) and six armoured trains; they managed to destroy 80% of the Dutch military aircraft on the ground in one morning, mostly by bombing. Although the Dutch army was inferior in nearly every way, consisting mostly of conscripts, poorly led, poorly outfitted and with poor communications, the Germans lost over 500 planes in the three days of the attack, a loss they would never replenish. Also the first large-scale paratroop attack in history failed, the Dutch managing to recapture the three German-occupied airfields near the Hague within the day. Remarkable was the existence of privately owned anti-aircraft guns. No less surprising may be the fact that the Dutch army owned only one tank.

The Dutch air force, which was not an independent arm of the Dutch armed forces, but part of the Army, on 10 May operated a fleet of 155 aircraft: 28 Fokker G.1 twin-engine destroyers; 31 Fokker D.XXI and seven Fokker D.XVII fighters; ten twin-engined Fokker T.V, fifteen Fokker C.X and 35 Fokker C.V light bombers, twelve Douglas DB-8 dive bombers (used as fighters) and seventeen Koolhoven FK-51 reconnaissance aircraft — thus 74 of the 155 aircraft were biplanes. Of these aircraft 125 were operational. Of the remainder the air force school used three Fokker D.XXI, six Fokker D.XVII, a single Fokker G.I, a single Fokker T.V and seven Fokker C.Vs, along with several training airplanes. Another forty operational aircraft served with the marine air service along with about an equal number of reserve and training craft.The production potential of the Dutch military aircraft industry, consisting of Fokker and Koolhoven, was not fully exploited due to budget limitations.