Battle of the Afsluitdijk The Battle of the Afsluitdijk was an unsuccessful attempt by the German Army to seize the Afsluitdijk in May 1940 , during World War II . If the Germans had taken the dyke , they could have taken North - Holland from its north . The Dutch troops were led by Captain Christiaan Boers and the Germans by General Kurt Feldt . Fortifications and preparations . Germany invaded the Netherlands on 10 May 1940 as part of plan " Fall Gelb " . They rapidly crossed two thin defence lines , the O - line and the Q - line which the Dutch had built to defend their three northern provinces . The German 1 . " Kavalleriedivision " — later reformed to the 24 . " Panzerdivision " — had taken the last Dutch defences in front of the Afsluitdijk ( Wonsline ) on 12 May and was prepared for an assault to take the two lines of pillboxes or casemate s of Fort Kornwerderzand ( named after a hamlet near the dyke ) . The eastern line was for defence eastward , while the western line was just behind the first for threats from the rear . Altogether , 17 casemates had been built . They were designed to withstand rounds ( indirect fire ) , and rounds ( indirect fire ) . The three main casemates were made of of reinforced concrete . The casemates sheltered 230 men , twenty - one Schwarzlose machine gun s , three guns and a 50 mm shore - based naval gun . There were similar defences at the other end of the dyke . The battle . Earlier in May 1940 , two infantry sections — 70 men in all — were sent to the end of the dyke to prevent German landings beyond the vision of both fortresses . The Germans soon found out about these units , and seven " Luftwaffe " fighter s strafed Dutch positions . One soldier and two civilians were killed , 10 civilians wounded . After this , they were recalled to Kornwerderzand . Until 12 May , the Germans had not tried to take Fort Kornwerderzand . However , that evening three soldiers were sent to see if the fort had been abandoned . They were pinned down by machine gun fire . Two were killed , while the third escaped . The Germans decided to take the fortress . They planned to launch " Luftwaffe " strikes , then an extended artillery bombardment by howitzer s , after which they would send 500 soldiers . However , unknown to the Germans three anti - aircraft cannon s and four heavy anti - aircraft machine guns had arrived overnight at Kornwerderzand . The next day , pilots who had previously flown unchallenged were under fire . The Germans sent 62 planes to bomb the fort . The planes dropped five waves of bombs . Four planes were shot down and crashed into the sea . The bombardment was followed by an hour of heavy bombardment from the howitzers , but it had little effect on the heavily protected Dutch . As soon as the bombing stopped the Germans advanced down the narrow dyke . Boers waited until they were within , then ordered machine - gun fire , making it difficult for the Germans to withdraw . Most soldiers tried to hide , while a few managed to advance . The Germans were under constant fire for an hour and 20 minutes . When Boers ordered firing to stop , the remaining Germans withdrew — the assault had failed . During the night Boers ordered the dyke to be lit by flares and search lights so the fortress could not be attacked by surprise . On the early morning of the 14th , the Germans once again fired their artillery at the fortress ; however , during the night the Dutch had called in the sloop , which returned fire with her three heavy guns from her position in the Wadden Sea approximately from the German positions . Fire directions came in from the fortress by telephone to Dutch Navy Command in Den Helder who forwarded them by radiotelegraph to the gunboat . This barrage silenced the German guns in less than an hour and dumbfounded the German commander , General Kurt Feldt , who was unaware of the presence of any Dutch artillery in the area , let alone this heavy caliber . Casualties . Local civilians said hundreds of Germans were killed , and the dyke was filled with bodies . The German report says two were killed on the 12th and three on the 13th . The German wounded were officially around 25 . The Dutch suffered one killed during the first attack by the Luftwaffe and two wounded during the bombing when two soldiers manning anti - aircraft guns were hit . Civilian casualties numbered at two killed , 10 wounded , all from the first Luftwaffe attack . Aftermath . The fortress remained in Dutch hands until the surrender of Dutch forces on 15 May . Boers told the men that they had fought like lions but that in other parts of the country , their armies had been defeated . Boers himself led the surrender .