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On 9 January 1917, the Kaiser met with Chancellor Bethmann-Hollweg and military leaders at Schloss Pless to discuss measures to resolve Germany's increasingly grim war situation; its military campaign in France had bogged down, and with Allied divisions outnumbering German ones by 190 to 150, there was a real possibility of a successful Allied offensive. Meanwhile, the German navy was bottled up in its home port of Kiel, and the British blockade had caused a food scarcity that was in turn causing deaths due to malnutrition. The military staff urged the Kaiser to unleash the submarine fleet on shipping travelling to Britain, Hindenburg advising the Kaiser that "The war must be brought to an end by whatever means as soon as possible." On 31 January, the Kaiser duly signed the order for unrestricted submarine warfare to resume effective 1 February; Bethmann-Hollweg, who had opposed the decision, said "Germany is finished".

On 27 January, Admiral Beatty observed that "The real crux lies in whether we blockade the enemy to his knees, or whether he does the same to us."

Germany would have 105 submarines ready for action on 1 February: 46 in the High Seas Fleet; 23 in Flanders; 23 in the Mediterranean; 10 in the Baltic; and 3 at Constantinople. Fresh construction ensured that, despite losses, at least 120 submarines would be available for the rest of 1917.

The German Navy how ever thought to need a better base near the North Sea. Flushing would be the best option for this. Although it entered Belgium in 1914 with a very weak causus beli it still needed a causus beli to invade the Netherlands. It found this in the confiscation of all the dutch merchant ships by the USA. Despite strong objection and demand to release the ships the Germans were in the impression that the Dutch were supporting the Allies.
The Dutch PM and secretary of foreign affairs tried to persuade the Germans that the Netherlands were still neutral, but in vain.
Already since 1917 the German Navy had made plans to invade the South of the Netherlands in order to control the Dutch Province of Zeeland and establish submarine bases in the Schelde estuary. Due to limit of sources the German Army could only deliver support units and initially a limited number of men. Due to the armistice of the East front several units were transferred tot he West in January 1918 and reinforced with recruits. Their main objective was central Netherlands.
The action in the South was nearly an entire Navy affair. The bulk of the men where sailors from surface ships, trained in land combat. The Navy units were reinforced with some experienced Army units who would act as the front troops.
The Dutch army nearly did not move since September 1914 with exception of the Island of Walcheren and the heights between Antwerp and Bergen-op-Zoom, a height which controlled the access to the Islands Beveland and Walcheren. On Walcheren, with the city Flushing was continue reinforced until 25000 men and the height near Antwerp was reinforced with ever extensive trench systems, who were under continues construction and improvement.

On the first of February still in the dark the Dutch border units guarding the railroad border crossing between Belgium and the Netherlands were attacked and quickly defeated a armored train steamed quickly North caring a company, followed by and other longer unarmed train with a complete battalion on-board. At the German- Dutch boarder North East the same happened. The trains from Belgium headed towards Flushing while the trains in the North East drove to the cities Zutphen, Zwolle, Deventer and Arnhem, with the objective to conquer the bridges crossing the river Ijssel.
The trains were followed by reinforcements on foot and artillery by horse.
Unfortunately for the Germans the train heading to Flushing was stopped by the heights near Antwerp and the trains with he Ijssel bridges as objective were stopped in front of the bridges by Dutch units of the 2nd division.
At the entire Ijssel front numerous battles took place with ended in the retreat of the 2nd division North after they destroyed all the bridges. The river Ijssel is a small narrow river, except during the winter when it double or even triple in with. The crossing of the river by small boats was not really a problem until the boats were half way then they were met by filed artillery from the high grounds West of the river. Eventually beachheads were formed but the low lands West of the river turned to be killing fields and West, parallel of the river the Canal Appeldoorn turned to be a 2nd make shift defense line. All in all it took nearly three day to cross and secure the river Ijssel. Two days later the Germans had to fight their way over the height East of the city Utrecht which took them an other two days before the Dutch army finally retreat behind the Water line. It took the Germans in the center seven days to chase the Dutch army behind the Waterline. The Dutch 2nd division finally retreat in relative good order with he help of hundreds of fishing ships across the Zuyderzee to the province of Holland.
In the South the advance did not worked as a clockwork for the Germans either. Despite the use of experienced front troops it took two days battle to defeat the Dutch on the height North of Antwerp and another four days fighting to secure the Islands of Tholen, Walcheren and Beveland.
On February the 10th the first German U-boat entered Flushing and left on patrol the 12th.

During this seven days war the Allies did not sent troops or support to the Dutch event he objective was after one day relatively clear. If Zeeland was occupied by the Germans they would have a much better base for U-boat operations.The only support came from the Royal Navy, when ships of the Dover squadron give artillery support to the Dutch troops.

On the 8th commonwealth troops disembarked in Rotterdam, which, but by then Zeeland was lost and the front at the Waterline secured. The Germans did one attempted to attack the line but were repulsed relative easy, after which the Germans did not tried it again. Offensive actions were by the Dutch, as the Allies were demanding, were rejected by the General commander General Snijders, even with Commonwealth reinforcements.
The Dutch cabinet now urged to give food support for the now beleaguered Dutch population in stead of reinforcements. It took considerable effort to feed the nearly 3 million people behind the Dutch Waterline.
This North sea crossings were now even more dangerous since the U-boat base in Flushing even most of the patrol area of the U-boats was South of Flushing.

At 21st March the Germans launched their spring offensive, operation Michael, whit much initial successes. However by exhaustion of German troops, attrition and sudden abundance of luxury food and drinks the Germans soldiers encountered the offensive lost its momentum. The British and French regrouped and adapted their defense. By beginning of April the German advance stopped.

In August the Allies launched their own offensive which saw the collapse of the German defense lines and resulted in a dynamic warfare which ended at 11 November 1918 with the armistice.
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