A domestic war became a trial run for the weapons and ideologies of World War II

From 1936 to 1939, Spain's elected Republican government fought Nationalist rebels led by Francisco Franco, who received troops and planes from Hitler and Mussolini while the Republicans drew volunteers and aid from the Soviet Union and international brigades. Franco's victory installed a dictatorship that lasted until his death in 1975.

— Wikipedia contributors, Spanish Civil War — Encyclopedia entry