Spain was neutral in WW1 and WW2 but experienced a civil war (1936-1939) which killed over 500,000 people.
The Spanish Civil War (Spanish: Guerra Civil Española) was a civil war in Spain fought from 1936 to 1939. Republicans loyal to the elected, left-leaning Second Spanish Republic, in alliance with anarchists, fought against a revolt by the Nationalists, an alliance of Falangists, monarchists, conservatives, and Catholics, led by a military group among whom General Francisco Franco soon achieved a preponderant role.
Due to the international political climate at the time, the war had many facets and was variously viewed as class struggle, a war of religion, a struggle between dictatorship and republican democracy, between revolution and counterrevolution, between fascism and communism. It has been frequently called the "dress rehearsal" for World War II.
The Nationalists won the war, which ended in early 1939, and ruled Spain until Franco's death in November 1975.