In 1936 when the Spanish Civil War erupted he found himself behind republican lines and had to sneak through the front in order to reach the nationalists. He then served in the nationalist navy. After the nationalist victory and the beginning of the dictatorship of Francisco Franco he became one of his closest collaborators as well a chief of naval operations. He was said to be in opposition to the entering of Spain along the Axis in WW2, in opposition to Falangists, himself being a monarchist.
He reached his highest position when he was named prime minister of Spain and likely successor to Franco in June 1973.
Eventually he was killed in Madrid by four Basque independentist from ETA who bombed his car while he returned from mass in an armored car, the bomb being in an underground tunnel they dug under the street. This assassination (dubbed Operación Ogro) was in retaliation of the mass execution of various political opponents by the regime including a large number of Basque.