The major conflict fought between the Axis and Allied powers from 1939 to 1945 was World War II. This global war was initiated by Germany's invasion of Poland, leading to widespread involvement from numerous countries across Europe, Asia, and beyond. The Axis powers, primarily comprised of Germany, Italy, and Japan, sought territorial expansion and dominance, while the Allies, including the United States, the Soviet Union, and the United Kingdom, fought to stop their aggression. The conflict resulted in unprecedented casualties, significant geopolitical changes, and the establishment of the United Nations, aimed at promoting international cooperation and preventing future wars.