On April 14, 1931 the Spanish monarchy was declared overthrown and a provisional government took power. In the ensuing years, the government became increasingly divided between the socialists of the extreme left and the monarchists of the extreme right. In the elections of February 1936 the left won a clear majority. The right reacted with fervor. Generals Goded, Mola, and Francisco Franco disagreed with the leftist efforts at army reform, and viewed with distaste the violence and anarchy which reigned in the streets of Spain. They decided to overthrow the government.
Mola organized for military action in Pamplona, while Franco traveled to Morocco to lead the African installment of the Spanish army against the republic. The military Nationalists pronounced their intentions on July 17, 1936. The rebels stirred by the Nationalists were easily defeated in many cities where the loyal Civil Guard was present. However, in cities unprotected by the Civil Guard, the Nationalists took control quickly, in many cases aided by supplies from Benito Mussolini and Adolf Hitler. The Republicans, aided by the Soviet Union, consolidated support for the republic, and by May 1937 were entrenched in defensive positions in a triangle of cities with the points in Madrid, Valencia, and Barcelona.
The Republicans tried to turn their rag-tag militia into an effective fighting force, beginning in October 1936 with the creation of the Popular Army, which, while better organized than the militias, was chronically short of arms and ammunition, and was beset by incompetent junior officers and political factions within the ranks. With only limited support from France, and none at all from Britain, The Spanish Republicans turned to the Soviet Union for support. Soviet tanks, superior to the German Mark IIs, arrived in October, along with advanced aircraft and Soviet military advisors. One source of support for the Republicans was the presence of the International Brigades. These groups of leftist volunteers were made up mostly of workers, who volunteered out of boredom, disillusionment, or a desire for adventure as often as genuine political idealism. The protagonist of Ernest Hemingway's For Whom the Bell Tolls is such an international brigadier. However, this support was not enough.
On April 25, 1937, the small northern town of Guernica was bombed by the Nationalists, and civilians were gunned down as they fled the scene. In this brutal massacre 1500 died and 800 were wounded, but the military targets in the town remained intact. As the bloody conflict escalated, the Republican government fell prey to corruption and faction, and support and organization steadily waned. Under the barrage of nationalist attack Barcelona fell, during January 1939. Catalonia fell during February, and Valencia and Madrid collapsed by the end of March. Franco's ensuing rein was one of oppression and tradition. He imprisoned and many upon coming to power--up to a million according to some estimates. Many fled Spain, becoming refugees and awaiting the toppling of the Franco government. They would wait for 36 years, for Franco remained in power until his death in 1975.
One major difference setting the Nationalists apart from the Republicans was leadership. Nationalist, fascist leadership proved more effective at carrying out the war than the clumsy democratic government of the Republicans. The Republican government in Madrid under Largo Cabellero was divided within itself, confused about its identity and ideology. The Nationalists had no such difficulties. When Franco was proclaimed head of the Nationalist government on September 29, 1936, there was no one to challenge his authority. Franco's wing of the army was the most successful of the nationalist forces, and he was a respected and very professional soldier. The Nationalists did experience some military problems similar to those of the Republicans. The command structure of the army had been destroyed by the division of the nation. Thus, the Nationalists suffered from incompetent junior officers, but not to the same extent as the Republicans.
Mussolini had been involved to some extent in Spanish affairs before the revolt, but he knew nothing of the generals' plans. He supported the rebels against the judgment of his military advisors, sending bombers and soldiers to Spain in great quantity. There were 50,000 Italian soldiers in Spain at the height of their involvement, and hundreds of airplanes were sent, along with tanks and artillery. The Germans were far less generous, but sent the famous Condor Legion of about 100 planes, which was largely responsible for the Guernica bombing. Germany also made a great contribution in the form of specialists and instructors.