On the 10th May 1936 the conservative Niceto Alcala Zamora was ousted as president and replaced by the left-wing Manuel Azaña. Soon afterwards Spanish Army officers, including Sanjurgo, Emilio Mola, Francisco Franco and Gonzalo Queipo de Llano, began plotting to overthrow the Popular Front government. This resulted in the outbreak of the Spanish Civil War on 17th July, 1936.
On 20th July 1936 Sanjuro was killed when his plane crashed. When General Emilio Mola was also killed in an aircraft accident, rumours began to circulate that General Francisco Franco was responsible for the deaths of his two fellow leaders. However, no evidence has ever been found to substantiate this accusation.