The church tower in the village of Midlum served as an observation post of the 14th Field Regiment Royal Canadian Artillery during the shelling. The tower was operated by several Canadian soldiers with a radio transmitter and staff maps. The German forces fired back from Harlingen and the tower was hit twice in the process, wounding the Canadian Lieutenant Colonel George Alleyne Browne and Lieutenant Gordon Edward Whitaker. The latter was injured on his spine, leaving him paralysed for life. He is honoured, along with the three Midlum residents who died during the war, on the war memorial near the village church. Browne, the commander of the 14th Field Regiment, was only slightly wounded and was able to resume his duties immediately. 

Additionally, an Auster reconnaissance aircraft was also used to make aerial observations. This was a small two-seater aircraft that could fly slowly and was therefore ideally suited for artillery reconnaissance. The pilot and the observer sat side by side and reported their observations to the fire chief by radio. The fire chief sat together with section commander Cleem Heeger in a jeep by the side of the road by a farm near the Old Station on the Harlingerstraatweg road just behind Midlum. Heeger later said of the reconnaissance plane that the reconnaissance plane flew so slowly that ‘it looked like it was standing still in the air’. 

The Canadian forces were able to carry out the shelling with such accuracy and focus was due in most part to the maps of Harlingen made by Arie Veth. The lead administrator of the Geheime Dienst Nederland (Secret Service Netherlands, Dutch Resistance group). J.C.A.H. van Stapele, who brought the maps to the Canadian forces, wrote in his report: ‘Thanks to the accurately mapped German artillery positions, the Canadian artillery did not have to make a mess of Harlingen, but forced the Germans to surrender with only a few well-aimed salvos’. 

Another reason the German positions could be quickly and effectively eliminated was the action of B Squadron of the 7th Reconnaissance Regiment Duke of York's Royal Canadian Hussars. By provoking German fire, the 7th Reconnaissance Regiment was able to establish some positions of the German forces from Midlum. The coordinates were passed on to the artillery. Commander Major Charles Wesley MacLean was awarded the Distinguished Service Order (DSO) on 10 November 1945 in part for this brave action at Midlum. 

The attack on Harlingen began just before the artillery was due to fall silent. From 20:00, infantry of the Highland Light Infantry of Canada, supported by tanks of the Canadian Sherbrooke Fusiliers, launched the attack. During heavy fighting, Canadian forces managed to penetrate the city centre around 22:30. By 04:30 on 17 April, the German forces in the city had been defeated. Around 500 of them were captured.