Who was major aggressor during World War 2?

The major aggressors during World War II were Nazi Germany, Imperial Japan, and Fascist Italy. Germany, under Adolf Hitler, initiated the conflict by invading Poland in 1939, while Japan sought to expand its empire in Asia, attacking China and later the United States at Pearl Harbor. Italy, led by Benito Mussolini, joined the Axis Powers and engaged in military campaigns in Africa and Europe. Together, these nations pursued aggressive expansionist policies that contributed significantly to the war's outbreak and escalation.