On July 17, 1936, a conspired military uprising broke out in the Spanish colony of Morocco. Within a month, the rebellion spread to mainland Spain, and over the next three years Spain became the center of a war between fascism and communism. With Nazi Germany and fascist Italy supporting the right-wing nationalists, and the Union of the Soviet Socialist Republic (Soviet Union) supporting the left-wing Republic, this conflict spanned all of Western Europe. When talking about foreign intervention in the Spanish Civil War, the major powers of Hitler, Mussolini and Stalin come to mind as the main contributors. However, the importance of the Soviet Union is often underestimated. Alongside the loyalists, the Soviets supported the republican government in the defense of Spain against the revolting fascist military. In particular, the Soviet Union played a crucial role in the defense of Madrid. First, the Soviet sent many advisors and specialists to provide advice, strategic military intelligence, and mental support to the loyalists. These Soviet men eventually took command of Madrid's forces and became the backbone of Madrid's operations. Second, the Soviets provided material aid in the form of tanks, planes, and weapons. These supplies gave Madrid's loyalists the firepower to resist the rebellious nationalists. Finally, the Soviets were responsible for the creation of the International Brigades (IB) which were the key forces in the defense of the three bridges leading to Madrid. The Soviet Union's intervention in Spain during the Spanish Civil War, particularly its role in the Battle of Madrid, provided the most essential support to the Republican forces in Madrid, allowing the Loyalists to hold off the Nationalist siege. ... middle of paper ......Web. May 18, 2014."Spanish Civil War." International encyclopedia of the social sciences. Ed. William A. Darity, Jr. 2nd ed. vol. 8. Detroit: Macmillan Reference USA, 2008. 42-44. Gale Virtual Reference Library. Network. April 29, 2014. “Spanish Civil War.” UXL Encyclopedia of United States History. Sonia Benson, Daniel E. Brannen, Jr. and Rebecca Valentine. vol. 7. Detroit: UXL, 2009. 1455-1456. Gale Virtual Reference Library. Network. April 29, 2014.Stalin, Giuseppe. "Madrid." Letter to the Central Committee of the PC of Spain. October 16, 1936. MS. Journal of Revolutionary Democracy, Moscow.Vincent, Mary. Constitutionalism and civil war 1812-1974. Cultural Atlas of Spain and Portugal. Oxfordshire: Andromela Oxford Limited, 1994. 152-61. Print.Whealey, Robert. "How Franco Financed His War: Reconsidered." Journal of contemporary history. Wise publications. 133-52. JSTOR. Network. May 5 2014.