The major global conflict that took place from 1939 to 1945 was World War II. This conflict involved most of the world's nations and was predominantly fought between two major alliances: the Allies and the Axis powers. The war was characterized by significant events such as the Holocaust, the use of atomic bombs, and the widespread battles across Europe, Asia, and the Pacific. It resulted in the loss of millions of lives and significant geopolitical changes, including the establishment of the United Nations and the beginning of the Cold War. The outcome fundamentally reshaped national borders and international relations.