[a][2] Although the state of hygiene in the building, which had been closed in 1930 was appalling, officials of the Prussian justice ministry recommended it as a suitable site.

Later, on the order of the head of the Prussian Gestapo, prisoners were deported from the penal institution of Gollnow (Goleniów) in Pomerania to Sonnenburg, bringing the number of inmates to 1,000.

Prisoners included Poles, Frenchmen, Luxembourgers, Dutchmen, Danes, Norwegians, Belgians, Czechs, Yugoslavs, Slovaks, Bulgarians, Austrians, the Swiss, Estonians, Russians and Spaniards.

On the night of 30–31 January 1945 with the Red Army approaching, the Gestapo killed over 800 prisoners by lining them up against a wall and shooting them.

During the early years of their rule, and long before the start of the war, the Nazi regime mainly imprisoned Communists and Social Democrats in Sonnenburg.