World War II: Adolf Hitler and Benito Mussolini meet at the Brenner Pass in the Alps and agree to form an alliance against France and the United Kingdom.

World War II or the Second World War was a global conflict between two coalitions: the Allies and the Axis powers. Nearly all of the world's countries participated, with many nations mobilising all resources in pursuit of total war. Tanks and aircraft played major roles, enabling the strategic bombing of cities and delivery of the first and only nuclear weapons ever used in war. World War II is the deadliest conflict in history, causing the death of 70 to 85 million people, more than half of whom were civilians. Millions died in genocides, including the Holocaust, and by massacres, starvation, and disease. After the Allied victory, Germany, Austria, Japan, and Korea were occupied, and German and Japanese leaders were tried for war crimes.

Adolf Hitler was an Austrian-born German politician who was the dictator of Germany during the Nazi period from 1933 until his suicide in 1945. He rose to power as the leader of the Nazi Party, becoming the chancellor in 1933 and then taking the title of Führer und Reichskanzler in 1934. His invasion of Poland on 1 September 1939 marked the start of the Second World War. He was closely involved in military operations throughout the war and was central to the perpetration of the Holocaust: the genocide of about six million Jews and millions of other victims.

Benito Amilcare Andrea Mussolini was an Italian politician and journalist who, upon assuming office as Prime Minister, became the dictator of Fascist Italy from the March on Rome in 1922 until his overthrow in 1943. He was also Duce of Italian fascism upon the establishment of the Italian Fasces of Combat in 1919, and held the title until his summary execution in 1945. He founded and led the National Fascist Party (PNF). As a dictator and founder of fascism, Mussolini inspired the international spread of fascism during the interwar period.