The German people and troops disliked the idea of going against Dutch neutrality. The Germans said the invasion was to stop the Allies from occupying the Low Countries. Some German officers did not like the Nazi government and were also unhappy with the invasion.
One of them was Colonel Hans Oster, a German intelligence officer. In March 1939 he began to pass information to his friend, a Dutch military officer in Berlin Major Gijsbertus J. Sas. This information included the German attack date. Sas informed the Allies. Sas knowing the date of the attack on Denmark and Norway was not noticed. Though he said a German armoured division would try to attack the Netherlands and that there was a plan to capture the Queen, the Dutch defence plan was not changed.
On 4 May Sas warned that an attack was coming soon. When in the evening of 9 May Oster phoned his friend saying the attack would be soon, the Dutch troops were put on alert.
Oster was a leader of the German resistance from 1938 to 1943, and was one of those hanged after the 20 July 1944 bomb plot to kill Hitler.
On the morning of 10 May 1940, Germany attacked the Netherlands, Belgium, France and Luxembourg.
In the night the Luftwaffe flew into Dutch lands. One group, "Kampfgeschwader 4" (KG 4), attacked the Dutch airfields. Led by "Oberst" (Colonel) Martin Fiebig, KG 4 attacked the naval airfield at De Kooy, destroying 35 aircraft. Fiebig was shot down and spent five days as a Dutch prisoner of war.
KG 4 also attacked Amsterdam-Schiphol, where the Dutch lost a third of their medium bombers, and The Hague airfields where KG 4 destroyed half of the 21 defending fighters. KG 4 lost 11 Heinkel He 111 bombers on 10 May and three Junkers Ju 88s; KG 30 and 54 another nine bombers. "Jagdgeschwader 26" (JG 26) and "Zerstörergeschwader 26" (ZG 26) shot down 25 Dutch aircraft for a loss of nine fighters, with Albert Kesselring's "Luftflotte 2" destroying 41.
The Dutch were left with just 70 aircraft by the end of the day. They continued to fight the "Luftwaffe", shooting down 13 German fighter aircraft by 14 May.
Paratroopers were landed near the airfields. Dutch anti-aircraft batteries shot down numerous Ju 52 transport planes. German Ju 52 losses in the battle were about 250 planes.
The attack on The Hague was a failure. The paratroopers did not capture the main airfield at Ypenburg in time for the airborne infantry to land in their Junkers. Five Landsverks, assisted by machine guns, destroyed the eighteen Junkers, killing many troops.
When the airstrip was blocked by wrecks the remaining planes landed in meadows or on the beach, spreading out the troops. The small airfield of Ockenburg was captured by the Germans.
The airfield of Valkenburg was occupied. However, the landing strip was still being built and the water level had not yet been lowered: planes landing there sank in the soft soil.
None of the airfields could be used to land new troops. The paratroopers occupied Ypenburg but did not get into The Hague. They were blocked by Dutch troops. Early in the afternoon they fired on by three Dutch artillery batteries. Dutch artillery drove away the German troops from the other two airfields.
The attack on Rotterdam was much more successful. Twelve Heinkel He 59 seaplanes landed in the city. They captured the Willemsbrug, a bridge over the Nieuwe Maas. At the same time the military airfield of Waalhaven was attacked by airborne forces.
Here an infantry battalion was close to the airfield. The paratroopers landed near them. A fight followed. The first group of Junkers suffered no losses and the transports continued to land. In the end the Dutch defenders were defeated. The Germans occupied IJsselmonde.
The Royal Netherlands Navy's torpedo boats "Z5" and "TM 51" attacked the "Willemsbrug". The destroyer HNLMS "Van Galen" sailed up the Nieuwe Waterweg to bomb the airfield, but the ship got bombed. A plan to send the gunboats HNLMS "Flores" and HNLMS "Johan Maurits van Nassau" was stopped.
At the Island of Dordrecht the Dordrecht bridge was captured but the Dutch fought on. The long Moerdijk bridges were captured and fortified on the southern side.
An armoured train crossed it followed by a troop train, which unloaded an infantry battalion behind the defence line.
Generally German soldiers behaved in a civilised manner towards the Dutch population, buying food at the shops.
After the failed assaults on the bridges, the German divisions began crossing over the rivers IJssel and Maas. The first attacks were destroyed by fire from the pillboxes.
At most places, bombing destroyed the pillboxes and the infantry divisions crossed the river by building pontoon bridges. At Arnhem, "Leibstandarte Der Fuehrer" led the attack and advanced to the Grebbe Line, followed by "207. Infanteriedivision".
A withdrawal was planned for the first night after the invasion, in the darkness. Due to the rapid German advance a quick retreat was ordered at 06:45. The corps joined "Brigade G", six battalions already occupying the Waal-Linge line.
The Light Division, based at Vught, was the only force the Dutch Army had that could move about. Its withdrawal had been done a day early. Its regiments had reached the Noord river in the evening.
Meanwhile, on the evening of the 10th, around 22:00, French troops using Panhard 178 armoured cars started to arrive at the Dutch border. After them, the French 1st Mechanised Light Division moved forward. Attempts to get the French to move forward with the Dutch troops towards Noord-Brabant did not work well.
When a first attack had been stopped, an attack at the Main Defense Line was postponed because most artillery had not arrived. In the early evening, they attacked even though there was only one 105 mm battery.
Colonel Schmidt at 20:30 ordered the Peel-Raam Position to be abandoned. He told his troops to go to the west at a new line at the Zuid-Willemsvaart canal.
In the North, by the end of the day, "1. Kavalleriedivision" had reached the line Meppel–Groningen. They were delayed by Dutch teams blowing up 236 bridges. Dutch troop strength in that area was weak.
In the south, the six border battalions in the province of Limburg delayed the advance of the German Sixth Army. Before noon Maastricht had surrendered. The Germans did not capture the main bridge intact. This delayed the crossing by the 4th Panzer Division until the next day.
On 11 May the Dutch commander General Winkelman had two goals. First of all he wanted to kill the German airborne troops. He thought that the German possession of the Moerdijk bridges would stop the movement of new Allied troops.
The second goal was to help the French army to make a strong defensive line in North Brabant.
Little was achieved this day. The attack by the Light Division against the airborne troops on IJsselmonde failed. The bridge over the river Noord was defended by the German paratroopers, and it was impossible to cross it. Several attempts to cross the river by boats were not that successful.
At 10:15, the Light Division was told to join the Dutch troops on the Island of Dordrecht. After killing German troops on the Island of Dordrecht the division was to advance into IJsselmonde over the Dordrecht bridge to reach Rotterdam.
Earlier during the day, two attempts were made by Dutch battalions to attack the western side of the German line. The First Battalion tried to attack the bridge at Barendrecht into IJsselmonde. The second battalion tried to capture more land.
Although its crossings were successful, the first battalion was attacked by the Germans. The second battalion had many men being taken prisoner.
Then a French force and another Dutch border battalion attacked the southern Moerdijk bridge, but the armoured cars were bombed by German Stukas and had to retreat.