Major engagement during the Battle of the Netherlands in WWII
The Battle of the Grebbeberg () was a major engagement during the Battle of the Netherlands, which was a part of the World War II Operation "Fall Gelb" in 1940.
Background.
In the 1930s, the Dutch government pursued a policy of strict neutrality. After World War I, the Dutch parliament supported a disarmament policy because it was generally thought that World War I had been "the war to end all wars". When the threat of Nazi Germany became more apparent the Dutch government decided to reinforce and retrain its Armed Forces. 
General defensive strategy.
In the 1930s the general defensive strategy was aimed at an attack by Germany. In that case the army should fall back on the Water Line, which formed part of Fortress Holland, the Dutch national redoubt. It was expected that assistance would then arrive from France and the United Kingdom. To defend the redoubt, it was necessary to slow the German advance in order to give as many Dutch forces as possible the chance of assembling in Fortress Holland. 
To this effect, several defensive lines had been constructed throughout the country. The Maas Line and the IJssel Line had been constructed along the Maas and IJssel rivers and served to detect German incursions into Dutch territory and to delay the Germans in the first hours of an invasion. The fortress at Kornwerderzand on the narrow Afsluitdijk guarded the northern approach to Fortress Holland while the Peel-Raam Line in North Brabant guarded the southern approach. Any attempt to approach Fortress Holland through the central part of the country would be delayed at the Grebbe line. 
At the beginning of 1940, Chief of Staff General Henri Winkelman redesignated the Grebbe Line the Main Defence Line, because defending the East Front of Fortress Holland would bring the major city of Utrecht into the frontline and the enemy too close to the Dutch capital Amsterdam.
The Grebbe Line.
The Grebbe Line was built in 1745 and had been used for the first time in 1794 against the French. It was maintained throughout the 19th century, but had been neglected ever since because it was thought to have become obsolete. In 1926, most fortifications were disbanded. When Germany became a potential threat the Dutch government had the Line recommissioned. 
At the end of the 1930s, a series of pillboxes and casemates were constructed in the area south of the IJsselmeer and north of the Rhine. The Line was constructed according to French military principles from World War I which had proven to be successful then, but had, unknown at the time of construction, become obsolete. There were major flaws in the design of the pillboxes, which were difficult to defend against attack from the flanks and rear. The (fixed) weapons were antiquated, many of them dating back to World War I. Because the Dutch government did not want to antagonise local residents, permission to remove buildings and trees in the line of fire was refused, which greatly reduced the effectiveness of the defences and gave attackers plenty of cover. The trench system was also based on World War I principles. It consisted of a line of outposts ("voorpostenlijn"), a Frontline ("frontlijn"), a Stopline ("stoplijn") and a Final Line ("ruglijn"). 
The position at the Grebbeberg suffered from a lack of serious security measures. The government did not want to interrupt tourism as the local economy of Rhenen was dependent on revenues from the Ouwehands Dierenpark, a zoo located on a hill near Rhenen, the Grebbeberg. In the months leading up to the invasion, German officers in civilian clothes visited the zoo and used its lookout tower to survey the local defences. The government estimated that the Line would be completed in November 1940 and in May 1940 the bomb-proof pumping station at the Grebbeberg—which was necessary for the control of local flooding—had not been completed. Because of the lack of inundation, the German spies realised that the Grebbeberg would be a vulnerable spot in the Grebbe Line.
The opposing forces.
The Grebbeberg was defended by the 8th Infantry Regiment (8 RI), Lieutenant Colonel Hennink. It was supported by a battalion of 19 RI. The defending units were part of the 4th division, Colonel van Loon. The 4th and 2nd division formed the 2nd army corps under Major General J. Harberts. On the Grebbeberg itself were 3 batteries of the 8th Artillery Regiment (8 RA), and three from the new 19 RA. Those of 8 RA were 1-I-8 RA and 2-I-8 RA armed with the 7 veld, and 2-III-8 RA with the 15 cm L/17 howitzer. Those of 19 RA were the three batteries of II-19 RA armed with the antique 12 cm Lang staal.
The German forces were the 207th Infantry Division (17,500 men) and the SS-Standarte Der Führer (c. 6,000 men). The 207th Infantry Division was a reserve unit that had only minimal combat experience. The SS was certainly elite, but its soldiers did not have any combat experience. These units were supported by about 50 guns. 
The battle.
At 03:55 local time on 10 May 1940, the German Army Group B invaded the Netherlands. The 207th Infantry Division—commanded by Karl von Tiedemann—and part of the 18th Army had been tasked with overrunning the Grebbeberg within a day. Resistance at the IJssel Line near Westervoort was fiercer than anticipated and it was dusk by the time the Germans had occupied Wageningen, the city directly to the east of the Grebbeberg. The 207th Infantry Division—reinforced with the SS-brigade "Der Führer"—made preparations to assault the hill next morning.
11 May.
The outposts fall.
In order to mount a direct assault on the Grebbeberg, the Germans had to breach the line of outposts ("voorpostenlijn") which covered a wide area directly in front of the Grebbeberg, which had not been flooded. The line was manned by two companies of the third battalion of the 8th Infantry Regiment (III-8 RI), which was part of the 4th Division and the 2nd Corps. In the early hours of 11 May, German artillery opened fire on the line of outposts, disabling the telephone system of the Dutch defenders. Now that communication with the other defensive lines had become impossible, the Dutch were deprived of artillery support. At dawn, the SS brigade launched a direct assault on the outposts. The defensive positions at the outposts were mostly improvised and consisted of sandbags and wooden obstacles. The field of fire of the Dutch defensive positions did not overlap. German forces were able to neutralise them one by one by sending two teams of machine gunners to attack a single position. One team would provide covering fire while the other would use the blind spots to launch a flanking attack.
In the northern part of the line, on the edge of the inundated area, the Germans ran into a section of the Dutch 19th Infantry Regiment (19 RI), which—because it was part of a different unit—had trouble co-ordinating its actions with the other Dutch positions. This section broke after a short skirmish and retreated westward, thereby creating an open flank which the Germans exploited by encircling the more southern Dutch sections. Near the Rhine the Germans used a dike to approach defending forces from the rear unhindered. Dutch supporting fire from the Frontline was largely ineffective because the area between the frontline and the line of outposts was carpeted in orchards, which kept the Germans out of sight. Now that the SS forces had succeeded in approaching the Dutch forces from the rear, the line of outposts could be neutralised. At 18:00, the last Dutch section surrendered and the "voorpostenlijn" fell into German hands.
The Dutch counterattack.
In the evening, German armored cars tried to attack the hill itself but were repelled by a anti-tank gun. That evening, Chris Meijer—an artillery sergeant who had been arrested for abandoning his post—was brought in and subjected to a court-martial and executed by firing squad. After the war, this court-martial would become controversial because of possible undue influence by the commander of 2nd Corps, General Harberts. This incident—and unfounded rumors of a massive rout in the line of outposts—incited Harberts into setting an example for other Dutch forces. At 21:00, he ordered the second battalion of 19 RI to initiate a counterattack under the cover of darkness against the outposts. Harberts estimated that about a hundred Germans were in the line of outposts, but in reality II-19 RI faced 3,000 SS troops. At the stopline, which was situated directly on the Grebbeberg, II-19 RI was fired upon by other Dutch troops who had not been informed of the impending counterattack. The confusion that followed caused the attack to lose momentum before it had made contact with the enemy and by the time order had been restored, dawn had broken and the counterattack was called off. One positive side-effect of the counterattack had been that Dutch artillery support forced the Germans to abandon their own planned night attack.
12 May.
Capture of the Frontline.
After the seizure of the outposts the previous day, the focus of the German force was on capturing the Frontline, which ran along the eastern slope of the Grebbeberg. Von Tiedemann decided to initiate a powerful attack on the hill. It was defended by four companies from II-8 RI and I-8 RI. They were reinforced by a machine gun company and an anti-tank unit which occupied the casemates nearby. There was a much larger number of Dutch machine guns in the frontline, so that this time there were no blind spots in which German units could hide. Von Tiedemann realised that an all-out assault like that of the day before would not work and ordered an artillery barrage which lasted for the better part of the morning. The artillery bombardment did not destroy the defensive works, but did undermine the morale of the Dutch units, which were mainly composed of conscripts.
After 12:40, the German guns ceased firing and the SS brigade attacked the "Hoornwerk", an 18th-century fortification which had to be seized first. The defenders' ammunition supply was low because of skirmishes with German forces the night before and in the early afternoon the Dutch started to give way. After a short engagement, the Hoornwerk fell and the Germans stormed the hill. The Germans threatened to out-flank the Dutch casemates which could only put fire onto the area directly in front of them. A fierce battle ensued on the wooded slope, but the automatic weapons of the SS gave them an advantage. The Dutch did not have sufficient forces in reserve to initiate a counterattack.
At 16:00, the Dutch troops at the Stopline on top of the Grebbeberg encountered the first German units. A frantic attempt was made to drive the Germans back to the Frontline, but the Dutch counteroffensive was no match for German firepower. North of the Rhenen-Wageningen road, Major Johan Henri Azon Jacometti—commander of II-8 RI—personally led a counterattack, but it failed after Jacometti was killed. To stall the German advance, reinforcements were necessary, and II-19 RI—the same battalion that executed the aborted counterattack the previous night—was ordered to advance to the Frontline. The battalion, however, suffered the same fate as the night before when nervous Dutch troops once again opened fire on the battalion. The demoralised soldiers withdrew to safety and the attack petered out.
Due to its concentration, the SS brigade became vulnerable to Dutch artillery. As the German advance was largely dependent on the strength of the SS brigade, the destruction of a large part of the brigade could turn the tide of the battle. However, the Dutch artillery—to avoid hitting their own troops—executed a mainly pre-arranged fire plan aimed at the interdiction of German reinforcements. Firing on the German concentration was limited to some individual commanders using their own initiative. There was also some effective fire from mortars.
Infiltration of the Stopline.
In the late afternoon and early evening, the SS brigade cleared the area between the Stopline and the Frontline of all resistance. By 20:00, the penetrated area was still quite limited with a depth of and a width of . There was no great higher level pressure on Von Tiedemann to make haste as the main German attack was near Rotterdam. The commander of the third battalion of the SS brigade—"Obersturmbannführer" (Lieutenant Colonel) Hilmar Wäckerle—was not satisfied with the limited progress and considered the