World War II explained to kids

World War II was a global war that lasted from 1939 to 1945. It involved most of the world's nations, including all of the great powers, eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. In a state of "total war", the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. Marked by mass deaths of civilians, including the Holocaust and the strategic bombing of industrial and population centres, it resulted in an estimated 50 million to 85 million fatalities. These made World War II the deadliest conflict in human history. The start of the war in Europe is generally held to be 1 September 1939, with the German invasion of Poland and subsequent declarations of war on Germany by France and the United Kingdom. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Under the Molotov–Ribbentrop Pact of August 1939, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Poland, Finland, Romania and the Baltic states. Following the onset of campaigns in North Africa and East Africa, the fall of France in mid-1940, and the Japanese attack on Pearl Harbor in December 1941, the war continued primarily between the European Axis powers and the British Empire, with battles taking place in North Africa, the Mediterranean, the Atlantic Ocean, the Middle East and Asia. The war in Europe concluded with an invasion of Germany by the Western Allies and the Soviet Union, culminating in the capture of Berlin by Soviet troops, the suicide of Adolf Hitler and the German unconditional surrender on 8 May 1945. Following the Potsdam Declaration by the Allies on 26 July 1945 and the refusal of Japan to surrender under its terms, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki on 6 and 9 August respectively. With an invasion of the Japanese archipelago imminent, the possibility of additional atomic bombings, and the Soviet entry into the war against Japan and its invasion of Manchuria, Japan announced its intention to surrender on 15 August 1945, cementing total victory in Asia for the Allies. Tribunals were set up by the Allies to try war criminals, and trials were held in Nuremberg, Germany. World War II changed the political alignment and social structure of the globe. The United Nations (UN) was established to foster international co-operation and prevent future conflicts. The victorious great powers—China, France, the Soviet Union, the United Kingdom, and the United States—became the permanent members of the United Nations Security Council. The United States emerged as a superpower, setting the stage for the Cold War, which lasted for the next 46 years. Meanwhile, the influence of European great powers waned, while the decolonisation of Asia and Africa began. Most countries whose industries had been damaged moved towards economic recovery. Political integration, especially in Europe, emerged as an effort to end pre-war enmities and create a common identity.