Originally a member of the Italian Socialist Party (PSI), Mussolini was expelled from the PSI due to his opposition to the party's stance on neutrality in World War I. Mussolini denounced the PSI, and later founded the fascist movement. Following the March on Rome in October 1922 he became the youngest Prime Minister in Italian history until the appointment of Matteo Renzi on February 2014. After destroying all political opposition through his secret police and outlawing labor strikes, Mussolini and his fascist followers consolidated their power through a series of laws that transformed the nation into a one-party dictatorship. Within five years he had established dictatorial authority by both legal and extraordinary means, aspiring to create a totalitarian state. Mussolini remained in power until he was deposed by King Victor Emmanuel III in 1943. A few months later, he became the leader of the Italian Social Republic, a German client regime in northern Italy; he held this post until his death in 1945.
Since 1939, Mussolini had sought to delay a major war in Europe until at least 1942. Germany invaded Poland on 1 September 1939, starting World War II. On 10 June 1940, Mussolini sided with Germany, though he was aware that Italy did not have the military capacity in 1940 to carry out a long war with France and the United Kingdom. Mussolini believed that after the imminent French surrender, Italy