The heavy cruiser "Prinz Eugen" in the port of Kiel, 1939
After 1933 Krupp is closely integrated in national socialist economic policy. In the effort to become self-sufficient, not only is indigenous coal used to produce fuel and oil but also the domestic ore basis is further expanded, with the Renn process developed by Krupp in 1929 permitting the reduction of low-grade ores.
Under the Four-Year Plan the state authorities intervene in the company's production planning. The production of locomotives, trucks and ships is strongly expanded and armaments production resumed, albeit on a much smaller scale than during World War One. The 80 cm railroad gun "Dora" completed in 1942, only two of which were ever produced, represents the biggest gun ever built but is already obsolete, being no match for aerial warfare. In 1938 the heavy cruiser "Prinz Eugen" is launched from the Germania shipyard, where many of the German submarines are also built during World War Two.