From October 1944, Crackstate prison had been the notorious headquarters of the men of the Sicherheitsdienst (Security Service, SD), who, chased by the Allies, moved north from Belgium. Countless prisoners were horribly abused, tortured, and even shot dead. At its peak, between 200 and 300 men and women were imprisoned there. Dozens of people were sometimes locked up in a five-person cell. A day before the liberation, the Germans threatened to blow up the entire complex. 

On 14 April, the Canadian liberators approached Heerenveen via Mildam. German troops were fighting stubbornly in the area, and there was heavy tank fire. The fifty or sixty inmates were trapped in terror in Crackstate, hearing the noise in the distance. Until baker Gerlof de Wolf and his helper Hendrik suspected around half past two that the enemy had left the city.   

De Wolf lived diagonally across from Crackstate and knew the situation well, and heard where the keys were. Mindful of bombs and booby traps, they crept cautiously through the open front door. They managed to get the prisoners out of the cells. Everyone left the prison in silence with orders to go into hiding as quickly as possible. Germans still appeared in the city every now and then. It remained dangerous. 
 
Reign of terror 

Before the SD, under the leadership of SS-Hauptsturmführer Kronberger, began its reign of terror, the resistance, six men strong, carried out a raid in September 1944. They managed to free two imprisoned "illegals." In March 1945, another raid was considered, but the risk was too great.  

A few days before the liberation, Kronberger received a threatening letter from the Dutch Domestic Armed Forces (NBS). It was the communist District Operations Leader (DOL) who warned him not to kill any more prisoners. A curious cat-and-mouse game between Kronberger and the District Operations Chief (DIC) imprisoned in Crackstate preceded this letter. 

Kronberger made a deal in exchange for release and a promise that the DIC and his deputy, the "communist" DOL, would return. The fear of the DOL's "Communist revenge" was apparently great. Since, of course, the DIC and DOL did not return, two prisoners at Luinjeberd were killed by the SD, the infamous German security service. More than sixty prisoners did not survive their stay in Crackstate because of torture, execution or transport to camps. After the war, Kronberger was sentenced to fourteen years of imprisonment. 

At the beginning of the evening of 14 April, the Canadians finally reached the southern part of Heerenveen. Around 19:00 hours, the residents welcomed the liberators with great cheer. Germans who remained behind suddenly opened fire at the partying crowd. There were no casualties. The next day, all of Heerenveen was liberated and 'traitors' and captured Germans were imprisoned in Crackstate. For some time, the Detention Centre served for the internment of NSB members. It was demolished in 1973, and a monument to the victims was unveiled in 1995.