World War I (1914–1918) was extremely destructive and led to the demise of the Austrian, German, Russian, and Turkish states. Most of these states had had monarchical systems of government, but there was a political vacuum in the postwar era. Those countries had lost the war, but even countries on the winning side of WWI were destabilized by the conflict.
Communists seized power in Russia in 1917. Fascism was, in part, a violent reaction against communism. Indeed, the communists who seized power in Russia promised to spread their system to every nation in the world.
Fascism appealed to many Italians after WWI. The country had gained very little from its sacrifices during the war, and social unrest was widespread. Italy's government was weak, and Benito Mussolini, leader of the National Fascist party, promised to save the country from both communism and anarchy.
In Germany, a fascist movement led by Adolph Hitler emerged after 1920. Germany lost the war, and its people were vengeful and dissatisfied with the country's postwar governments. In addition, the economy collapsed with the rise of high inflation and mass unemployment. Hitler became the leader of Germany in 1933.
Germany and Italy helped to create another fascist state in Spain during the Spanish Civil War (1936–1939). Fascist Francisco Franco won the war and became Spain's dictator.
Fascism was defeated in World War II, and both Mussolini and Hitler died in the last year of that war.