On July 17, 1936, the Spanish Civil War begins as a revolt by right-wing Spanish military officers in Spanish Morocco and spreads to mainland Spain. From the Canary Islands, General Francisco Franco broadcasts a message calling for all army officers to join the uprising and overthrow Spain’s leftist Republican government. Within three days, the rebels captured Morocco, much of northern Spain, and several key cities in the south. The Republicans succeeded in putting down the uprising in other areas, including Madrid, Spain’s capital. The Republicans and the Nationalists, as the rebels were called, then proceeded to secure their respective territories by executing thousands of suspected political opponents. Meanwhile, Franco flew to Morocco and prepared to bring the Army of Africa over to the mainland.

In 1931, Spanish King Alfonso XIII authorized elections to decide the government of Spain, and voters overwhelmingly chose to abolish the monarchy in favor of a liberal republic. Alfonso went into exile, and the Second Republic, initially dominated by middle-class liberals and moderate socialists, was proclaimed. During the first two years of the Republic, organized labor and leftist radicals forced widespread liberal reforms, and the independence-minded region of Catalonia and the Basque provinces achieved virtual autonomy.

The landed aristocracy, the church and a large military clique opposed the Republic, and in November 1933 conservative forces regained control of the government in elections. In response, socialists launched a revolution in the mining districts of Asturias, and Catalan nationalists rebelled in Barcelona. General Franco crushed the so-called October Revolution on behalf of the conservative government, and in 1935 he was appointed army chief of staff. In February 1936, new elections brought the Popular Front, a leftist coalition, to power, and Franco, a strict monarchist, was sent to an obscure command in the Canary Islands off Africa.

Fearing that the liberal government would give way to Marxist revolution, army officers conspired to seize power. After a period of hesitation, Franco agreed to join the military conspiracy, which was scheduled to begin in Morocco at 5 a.m. on July 18 and then in Spain 24 hours later. The difference in time was to allow the Army of Africa time to secure Morocco before being transported to Spain’s Andalusian coast by the navy.

On the afternoon of July 17, the plan for the next morning was discovered in the Moroccan town of Melilla, and the rebels were forced into premature action. Melilla, Ceuta, and Tetuan were soon in the hands of the Nationalists, who were aided by conservative Moroccan troops that also opposed the leftist government in Madrid. The Republican government learned of the revolt soon after it broke out but took few actions to prevent its spread to the mainland.

The following day, Spanish garrisons rose up in revolt all across Spain. Workers and peasants fought the uprising, but in many cities the Republican government denied them weapons, and the Nationalists soon gained control. In conservative regions, such as Old Castile and Navarre, the Nationalists seized control with little bloodshed, but in other regions, such as the fiercely independent city of Bilbao, they didn’t dare leave their garrisons. The Nationalist revolt in the Spanish navy largely failed, and warships run by committees of sailors were instrumental in securing a number of coastal cities for the Republic. Nevertheless, Franco managed to ferry his Army of Africa over from Morocco, and during the next few months Nationalist forces rapidly overran much of the Republican-controlled areas in central and northern Spain. Madrid was put under siege in November.

During 1937, Franco unified the Nationalist forces under the command of the Falange, Spain’s fascist party, while the Republicans fell under the sway of the communists. Germany and Italy aided Franco with an abundance of planes, tanks, and arms, while the Soviet Union aided the Republican side. In addition, thousands of communists and other radicals from France, the USSR, America, and elsewhere formed the International Brigades to aid the Republican cause. The most significant contribution of these foreign units was the successful defense of Madrid until the end of the war.

In June 1938, the Nationalists drove to the Mediterranean Sea and cut Republican territory in two. Later in the year, Franco mounted a major offensive against Catalonia. In January 1939, its capital, Barcelona, was captured, and soon after, the rest of Catalonia fell. With the Republican cause all but lost, its leaders attempted to negotiate a peace, but Franco refused. On March 28, 1939, the Republicans finally surrendered Madrid, bringing the Spanish Civil War to an end. Up to a million lives were lost in the conflict, the most devastating in Spanish history. Franco subsequently served as dictator of Spain until his death in 1975.