SS troops training area "Seelager" and memorial to the prisoners of the concentration camp
Memorial site

At the end of 1943, the Nazi German occupation authorities, planning to expand the SS motorised weapons units, started to build a training ground called "Seelager" (Sea Camp) in the vicinity of Dundaga. The inhabitants of the parishes of Dundaga and Arlava were evacuated to set up the training ground. 

In order to build the infrastructure for the camp, several branches of the concentration camp "Kaiserwald" were located in the vicinity of Dundaga, where around 6000 Jews from various European countries (including Latvia) and around 1000 prisoners of war and partisans were imprisoned. Many prisoners died as a result of executions and poor living conditions. Some of the dead were buried in the "Čiekuri" branch camp, which according to some accounts was also the murder site of a group of Jews who were building a narrow-gauge railway towards Mazirbe.

At the beginning of August 1944, after the Soviet invasion of Zemgale, the training ground was liquidated, several thousand untrained SS recruits were sent back to Germany, and the SS motorised brigade Gross was formed from the command, instructors and trained soldiers, named after the commander of the training ground, SS Standard-Sergeant Martin Gross. The Brigade took part in the Battle of Tukums in August 1944, and in the Battles of Iecava and Baldone in September 1944.

After the departure of the SS units, the infrastructure of the training ground was used to accommodate Jews evacuated from Riga and other regions of Latvia, who continued to be used as slave labour.