The Second World War, also known as World War II, was a global conflict that lasted from 1939 to 1945. It involved many of the world's nations, including all the great powers, which eventually formed two opposing military alliances: the Allies and the Axis. The war was marked by significant events such as the Holocaust, the use of atomic bombs, and widespread devastation across Europe, Asia, and other regions. It is considered one of the deadliest conflicts in human history, leading to profound changes in global politics, society, and the balance of power.