The Detention Centre, the Blokhuispoort, kept important resistance fighters in confinement. If they succumbed to the heavy pressure of interrogations and started naming names, many resistance fighters in the province would be in great danger. 

The leadership of the KP in Friesland had been devising a plan to raid the House of Detention since October 1944. The decision to take action fell in early December 1944. Immediately, it was also decided which prisoners would be free and which would be left behind. 

Using forged papers, the first group of KP members, including the leader of the action Piet Oberman, managed to enter the Detention Centre. The guards were overpowered, and the other members went inside. In minutes, the prisoners were freed from their cells. When three more prisoners were brought in by the occupying soldiers in the middle of the raid, things got exciting. Through quick action by the KP agents, they managed to lock up the escorts and free the detainees.  

Without a shot being fired, a total of 51 people were freed from the Detention Centre: 50 prisoners and one guard. The Germans responded on 9 December with intensive checks and house searches. The result was nil, no arrests were made and, quite exceptionally, no reprisals followed.  

After the war, the raid became one of the most famous actions of the Frisian resistance. Several books about the action appeared over the years. The 1962 film The Silent Raid made the story known across the country. Some one-and-a-half million cinemagoers watched this film.