Military production during World War II in the context of "Siege of Leningrad"

Air warfare was a major component in all theaters of World War II and, together with anti-aircraft warfare, consumed a large fraction of the industrial output of the major powers. Germany and Japan depended on air forces that were closely integrated with land and naval forces; the Axis powers downplayed the advantage of fleets of strategic bombers and were late in appreciating the need to defend against Allied strategic bombing. By contrast, Britain and the United States took an approach that greatly emphasized strategic bombing and (to a lesser degree) tactical control of the battlefield by air as well as adequate air defenses. Both Britain and the U.S. built substantially larger strategic forces of large, long-range bombers. Simultaneously, they built tactical air forces that could win air superiority over the battlefields, thereby giving vital assistance to ground troops. The U.S. Navy and Royal Navy also built a powerful naval-air component based on aircraft carriers, as did the Imperial Japanese Navy; these played the central role in the war at sea.

When the United Kingdom declared war on Nazi Germany in September 1939 at the start of World War II, it controlled to varying degrees numerous crown colonies, protectorates, and India. It also maintained strong political ties to four of the five independent Dominions—Australia, Canada, South Africa, and New Zealand—as co-members (with the UK) of the British Commonwealth. In 1939 the British Empire and the Commonwealth together comprised a global power, with direct or de facto political and economic control of 25% of the world's population, and of 30% of its land mass.

The contribution of the British Empire and Commonwealth in terms of manpower and materiel was critical to the Allied war-effort. From September 1939 to mid-1942, the UK led Allied efforts in multiple global military theatres. Commonwealth, Colonial and Imperial Indian forces, totalling close to 15 million serving men and women, fought the German, Italian, Japanese and other Axis armies, air-forces and navies across Europe, Africa, Asia, and in the Mediterranean Sea and the Atlantic, Indian, Pacific and Arctic Oceans. Commonwealth forces based in Britain operated across Northwestern Europe in the effort to slow or stop Axis advances. Commonwealth airforces fought the Luftwaffe to a standstill over Britain, and Commonwealth armies defeated Italian forces in East Africa and North Africa and occupied several overseas colonies of German-occupied European nations. Following successful engagements against Axis forces, Commonwealth troops invaded and occupied Libya, Italian Somaliland, Eritrea, Ethiopia, Iran, Iraq, Syria, Lebanon, Iceland, the Faroe Islands, and Madagascar.