The Spanish Civil War raged across the country from July 17, 1936 to April 1, 1939. It began with an only-partially-successful coup by military leaders against the democratically elected government. The coup forces, led by Generalissimo Francisco Franco, were supported by the fascist regimes in Europe, while the government had the support of the Soviet Union. The United States remained neutral, which had the effect of benefiting the rebels.
Many of the Left supported the Spanish government and some went to Spain to fight on its behalf. Ernest Hemingway went to Spain as a war reporter for the North American Newspaper Alliance. He later wrote the novel For Whom the Bell Tolls based on his time in Spain.
Combat in Spain allowed both the Nazis and the USSR to test weapons and tactics that would be used later. The Nazi air bombardment of Guernica, in the Basque region, has been viewed as a practice drill for the aerial bombing of World War II.
The war ended with Franco conquering Madrid in early 1939. Reprisals against republican supporters included the execution of tens of thousands of people.