For Germany to build its twelve synthetic oil plants with a capacity of 3.3 million tons a year required 2.3 million tons of structural steel and 7.5 million man-days of labor. (Britain imported all its oil from Iraq, Persia and North America). To overcome this problem, Germany employed millions of forced laborers and POWs; by 1944, they had brought in more than five million civilian workers and nearly two million prisoners of war—a total of 7.13 million foreign workers.