For Himmler and the SS, concentration camps were also of great economic importance. Prisoners had to do physically demanding and often dangerous forced labor, and after the war broke out, they were increasingly employed in the armaments industry. After the camps were put under the control of the SS Economic and Administrative Main Office [SS-Wirtschafts- und Verwaltungshauptamt or WVHA], the economic exploitation of prisoners only increased. Prisoners employed in the production of German war materials and armaments were worked to death in ever greater numbers.