Pozas briefly served as Minister of the Interior before being put in command of the Army of the Center, in October 1936. Nearly overwhelmed along the Jarama in February 1937, the Army of the Centre ultimately flung back the Nationalist pincers closing around Madrid after a bloody campaign culminating in the Battle of Guadalajara. In May Pozas, who has been appointed commander of the Army of the East, led a costly attack toward Huesca that cost the Republic 10,000 casualties. Pozas led the Republican Army of the East at Belchite and Teruel. It is said that during the war he also joined the PSUC) though pro-Soviet sources reject this claim.