To what degree were the U.S., Great Britain, Germany, the USSR, and Japan successful in regards to their efforts in economic mobilization during the war? What problems did they face?
This is an enormous question that can't really be answered fully in this small space. But a few generalizations can be made. Both Germany and Japan had put their economies on a war footing years before the actual outbreak of hostilities. An important factor to remember with respect to the German economy was that they used massive slave labor forces, as did the Japanese in China. The Soviet Union, having been accustomed to massive mobilization efforts during the 1930s, were nevertheless forced to cope with massive destruction of crops in the path of the German invasion. One of the most significant feats of Soviet mobilization was their relocation of industrial complexes from the west, where they were threatened by Hitler's armies, to the east, particularly Siberia. Both Great Britain and the United States were very successful in mobilizing both public opinion and industry to the war effort, largely framing it wartime programs in the context of the social welfare initiatives of the 1930s. These efforts took the form of rationing and in many cases the nationalization of and imposition of quotas on crucial industries. An interesting byproduct of this mobilzation was the entrance of millions of women and minorities into the workforce, most famously in the United States, but also in other countries, particularly the Soviet Union. While it is difficult to know in the case of the Soviet Union, most of the warring nations devoted over half of their spending to the war.