in late 1938 and early 1939 , the continuing economic crisis caused by problems of rearmament , especially the shortage of foreign hard currencies needed to pay for raw materials germany lacked , together with reports from gring that the four year plan was hopelessly behind schedule , forced hitler in january 1939 to reluctantly order major defense cuts with the wehrmacht having its steel allocations cut by 30 % , aluminum 47 % , cement 25 % , rubber 14 % and copper 20 % .