The Dutch Domestic Armed Forces (NBS) play a major role in the liberation of Friesland. The NBS in Friesland consisted (from December 1944) of the resistance groups of the KP ("Knokploegen", assault groups), LO (National Organisation for Aid to people in Hiding) and OD (Order Service).  

Such an underground army needed weapons, of course. 2,500 to 3,000 NBS personnel would be given weapons for the planned acts of sabotage, the occupation of bridges and locks, and capturing the enemy. From pistols and machine guns to sten guns. 

The weapons literally fell from the sky. From October 1944, Stirling and Halifax bombers flew from England in the direction of Friesland 47 times. At least 24 successful arms drops were carried out at some 14 places in the province. The bombers dropped containers of weapons, ammunition and explosives with parachutes above the Frisian meadows. Groups of NBS operatives would stand ready at night to indicate the drop zone with light signals and then transport and hide the weapons. 

Near Tritzum, just east of here, one successful drop by a Stirling bomber took place on the night of 10 to 11 April 1945. On its way back to England, it crashed into the North Sea off the Wadden Islands, presumably shot down by German flak. One of the crew members is buried on Terschelling, the others are still missing.  

Through secret transmitters, phrases indicating where and when a drop would take place would be exchanged with London. To liaise between England and the resistance over the drops, Prince Bernhard, as commander-in-chief of the NBS, sends two secret agents from the Bureau Bijzondere Opdrachten (BBO, "Office of Special Assignments") to Friesland. Together with marconist Alfred Springgate and their radio transmitter, Lykele Faber and Peter Tazelaar hid for a long time (from November 1944), in a yacht on the small lake Nannewiid near Oudehaske in southern Friesland.  

Meanwhile, commandos N. De Koning and R. Groenewoud travelled around the province with fake papers to give weapons training. They were previously dropped from England over Drenthe and brought to Friesland by the KP. 

Arms drops and the hiding of the weapons regularly led to life-threatening situations. The occupiers were fiercely hunting for hidden weapons. Possession of a weapon was a capital offence. A drop at Aalsum near Dokkum indirectly led to the largest mass execution in Friesland of twenty men in Dokkum. 

On Sunday, 8 April, "Radio Orange" relayed the long-awaited phrase via the BBC: "the bottle is empty." For the NBS, this was the signal to start sabotage operations 36 hours later. Canadian troops were almost at the border of Friesland. Weapons were taken out of storage. The NBS groups met at secret locations, and weapons and ammunition were distributed. 

The resistance groups already largely controlled Friesland before the arrival of the Canadians. Only at Harlingen-Makkum did the Germans place artillery for the defence of the Afsluitdijk, and the Canadians had to put up with heavy fighting. Mainland Friesland was completely liberated on 18 April.