Benito Mussolini's impact on world history was substantial, both as an early leader of European fascism and as an inspiration for Adolph Hitler.
Leader of the National Fascist Party, Mussolini became Italy's prime minister in 1922. He had been an elected member of the Italian Parliament, but his fealty to democratic processes ended there. Upon ascending to the prime ministership, Mussolini consolidated political power while marginalizing other political parties. As prime minister, he forced into effect laws institutionalizing one-party rule and laid the foundation for the fascist model that inspired Hitler. Using the usual instruments of dictatorial power, mainly secret police and party thugs, he ruthlessly sought to forge an Italy reminiscent of Imperial Rome, including the expansion of territory and acquisition of colonies in an effort at regaining the notion of a great empire, mostly at the expense of Ethiopia, which was invaded by Italian forces in 1935.
Mussolini's military support of the fascist forces of Francisco Franco during the Spanish Civil War (1936-1939) further endeared him to National Socialist movements throughout Europe, and reinforced his willingness to go against Great Britain and France while allying himself with Nazi Germany.
Unfortunately for Mussolini, and for Italy, his ambitions greatly exceeded his capabilities. Hitler, who had been elected chancellor of Germany in 1933, began to view his one-time role model with diminishing regard. The German-Italian "Pact of Steel," the alliance formalized in 1939, was clearly a one-sided alliance, with German forces having to ensure Mussolini's successes.
With Italy's defeat in World War II, Mussolini's reign ended. He would eventually be captured by Italian partisans, executed, and his body hung in public as the ultimate show of disrespect.
In short, Mussolini's historical significance resides in his role as an early proponent of fascism, whose visions for Italy and the world helped to bring about the most devastating conflict in world history.