The battle to liberate the north of the Netherlands progressed. Assen was liberated 12 to 13 April 1945 and in the city of Groningen German troops ceased fighting on 16 April. Nevertheless, it was not over yet. The occupying forces held out for a long time in Delfzijl. The town was easy to defend because of the flat land with good visibility and little cover, and the many ditches, canals, lakes and flooded areas were also useful. The German defence of the surrounded area, the 'Delfzijl Pocket', was aimed at catching fleeing, German soldiers. These had been driven forward by the Canadian troops' advance and wanted to be ferried across to the other side of the River Ems to Germany.

At the time, the Polish and Canadian forces did not succeed in advancing towards Delfzijl, and they got no further than Noordbroek. From there, they moved in three directions. One group went to Siddeburen, which was liberated without a struggle on 15 April.

In Siddeburen, a Canadian unit of about 25 soldiers withdrew for recuperation leave in Zuidlaren. A handful of Polish soldiers were left to secure the village against German punctures. The Polish troops were billeted in café De Witte Linden and had their attention focused on the northern edge of the village. The local resistance was asked to help guard the village at night. A defence plan was drawn up in the café, which was converted into a command post.

This proved to indeed be necessary, as on the night before the Führer's birthday (20 April), a German combat group snuck into Siddeburen from Tjuchem, Meedhuizen and Wagenborgen. They were well armed with anti-tank grenades and flares, among other things. In the middle of the night, fighting broke out throughout the village. Ground attacks were supported by artillery shells fired from the Wagenborgen and Delfzijl area. That night, Corporal Kazimierz Zalcer and soldiers Janusz Wisniewski and Karol Pryszcz were killed. Only at dawn did the German forces retreat.

Two members of the resistance were also ultimately killed: Jan Oostindiër and Willem Balkema. Their names are on the monument on Viskenijstraat in Siddeburen.