On Friday afternoon, 13 April 1945, the Leeuwarden headquarters of the resistance received the order to act openly against the enemy. Over the course of the evening, the five NBS groups of the municipality of Kollumerland-Nieuwkruisland gathered under the leadership of Municipal Operation Leader (Gemol) Ganzinga on Piebe Bakker's farm. Weapons and ammunition had been distributed, and they were ordered to take the locks of Dokkumer Nieuwe Zijlen. A detachment of Germans kept this entrance to the Wadden Sea well occupied during the war. 

The Wadden Sea and Lauwerszee area was of strategic importance. It was part of the German defence line, the Atlantic Wall. This bulwark ran along the coasts of France to Norway. At that time, the Lauwerszee was not yet closed off from the Wadden Sea, and the locks of Dokkumer Nieuwe Zijlen gave direct access to the sea and the Wadden Islands. 

At night, the battle groups advanced on the locks. A number of men crossed the water to attack from the other bank as well. Things went wrong when a shot was fired too early and the Germans were alerted. Shots were fired from all sides, forcing the battle groups to retreat. Meanwhile, the Germans left their positions, and the next morning the Dutch flag was hoisted on the locks without a fight. 

Part of the battle groups then took up positions at a crossroads not far from the locks. These were the roads along which the fleeing enemy tried to escape. In the course of Saturday morning, the first exchanges of fire already took place and the first arrests were made. In the days that followed, more and more occupiers tried to escape from Groningen to the West. The road to Germany was cut off. Motorcycles, buses and trucks passed the crossroads at the Soensterdijk. There were four fatalities on the side of the NBS in three days. The number of casualties (approx. 23) and prisoners (approx. 175) among Landwachters and Germans was considerably higher. 

On Sunday, the fighting was so heavy that Canadian carriers were called in for help. From Dokkum, which had been liberated the evening before, the armoured vehicles came to the locks via Kollum during the morning to offer help. The fight was soon over, and dozens of prisoners were transferred from the locks to Kollum in the afternoon. 

During the following days, several NBS members left the locks for nearby Oostmahorn to defend the port together with the Canadians against the attack of the German occupying forces from the island of Schiermonnikoog. 

In 1950, a monument was erected on the Soensterdijk in memory of the NBS members who died and the resistance. Every year, the fallen are commemorated here.