The Second World War was a conflict of staggering scale, one that reshaped the global order and left a legacy of both profound destruction and remarkable transformation. Its roots lay in the unresolved grievances of the First World War and the aggressive expansionism of Nazi Germany, Imperial Japan, and Fascist Italy. The war's cost in human life, estimated at 70 to 85 million people, was unlike anything the world had ever seen, with the Soviet Union alone losing an estimated 24 to 27 million citizens.
The war in Europe unfolded through a series of dramatic turning points. After the fall of France, the Battle of Britain and the German invasion of the Soviet Union in June 1941 set the stage for a brutal ideological conflict in the East. The German advance was ultimately blunted and reversed at the gates of Moscow and, most decisively, at Stalingrad, where the encirclement and surrender of the German Sixth Army in February 1943 shattered the myth of German invincibility. The subsequent Battle of Kursk, the largest tank battle in history, marked the final German strategic offensive in the East, after which the Red Army began its remorseless advance westward.
The war also saw the systematic murder of six million European Jews and millions of others in the Holocaust, a genocide of a scale and mechanized efficiency that remains historically distinct. The liberation of camps like Majdanek and Auschwitz in 1944 and 1945 revealed the full horror of the Nazi crimes to the world. The war's end brought the Nuremberg Trials, where surviving Nazi leaders were held accountable for crimes against humanity, though the pursuit of justice was uneven, with many perpetrators escaping punishment and some, like the camp doctor Josef Mengele, evading capture for life.
In the Pacific, the war was characterized by a brutal island-hopping campaign. The battles for Iwo Jima and Okinawa in 1945 demonstrated the fanatical resistance the Japanese were willing to offer, with staggering casualties on both sides. The use of the atomic bombs on Hiroshima and Nagasaki in August 1945, alongside the Soviet declaration of war, finally compelled Japan to surrender, ending the war. The war's conclusion also set the stage for the Cold War, as the United States and the Soviet Union emerged as superpowers with competing ideologies, and the decolonization of Asia and Africa accelerated in the following decades. The war's legacy, including the development of nuclear weapons and the founding of the United Nations, continues to shape the world today.