The Second World War was history's largest and most significant armed conflict. It served as the breeding ground for the modern structure of security and intelligence, and for the postwar balance of power that formed the framework for the Cold War. Weapons, materiel, and actual combat, though vital to the Allies' victory over the Axis, did not alone win the war. To a great extent, victory was forged in the work of British and American intelligence services, who ultimately overcame their foes' efforts. Underlying the war of guns and planes was a war of ideas, images, words, and impressions—intangible artifacts of civilization that yielded enormous tangible impact for the peoples of Europe, east Asia, and other regions of the world.
Scope and Consequences of the WarThe war pitted some 50 Allied nations, most notable among which were the United States, United Kingdom, Soviet Union, and China, against the Axis nations. The name "Axis," a reference to the straight geographic line between the capital cities of Rome and Berlin, came from a pact signed by Germany and Italy in 1936, to which Japan became a signatory in 1940. Ultimately a number of other nations would, either willingly or unwillingly, throw in their lot with the Axis, but Germany and Japan remained the principal powers in this alliance.
Although the roots of the conflict lay before the 1930s, hostilities officially began with the German invasion of Poland on September 1, 1939, and ended with the Japanese surrender to the United States six years and one day later. The war can be divided into three phases: 1939–41, when Axis victory seemed imminent; 1941–43, when Axis conquests reached their high point even as the tide turned with the U.S. and Soviet entry into the war; and 1943–45, as the Allies beat back and ultimately defeated the Axis.
Over those six years, armies, navies, air units, guerrilla forces, and clandestine units would fight across millions of square miles of sea and land, from Norway's North Cape to the Solomon Islands, and from Iran to Alaska. The war would include more than a dozen significant theatres in western Europe, the north Atlantic, Italy, eastern and southern Europe, Russia, North Africa, China, southern Asia, Southeast Asia, and the Pacific islands. Less major, but still significant, engagements took place in East Africa, the Middle East, and West Africa. There were even extremely limited engagements—mostly at the level of diplomacy, espionage, or propaganda—in South America and southern Africa.
Death toll. World War II and its attendant atrocities would exact an unparalleled human toll, estimated at 50 million military and civilian lives lost. Combat deaths alone add up to about 19 million, with the largest share of this accounted for by 10 million Soviet, 3.5 million German, 2 million Chinese, and 1.5 million Japanese deaths. (The United States lost about 400,000, and the United Kingdom some 280,000.)
Adolf Hitler and the Nazis killed another 15.5 million in a massive campaign of genocide that included the "Final Solution," whereby some 6 million Jews were killed. Another 3 million Soviet prisoners of war, along with smaller numbers of Gypsies, homosexuals, handicapped persons, political prisoners, and other civilians rounded out the total. Principal among the Nazi executioners was the SS, led by Heinrich Himmler, which operated a network of slave-labor and extermination camps throughout central and eastern Europe.
About 14 million civilian deaths have been attributed to the Japanese. They imposed a system of forced labor on the peoples of the region they dubbed the "Greater East Asia Co-Prosperity Sphere," and literally worked millions of civilians and prisoners of war (POWs) to death in their camps. The Japanese also conducted massacres of civilians that rivaled those undertaken by the Nazis in Russia.