He attended military college and entered the Paraguayan Army in 1922. He participated in the Chaco War and was appointed the Army's Chief of Staff in 1936. Morínigo gained fame in Paraguay during the February Revolution of 1936 by heading an expedition to the site of the Battle of Cerro Corá to retrieve the remains of Francisco Solano López. President José Félix Estigarribia, himself a Chaco War hero and supporter of the Liberal Party, promoted Morínigo to general and appointed him as Minister of War on May 2, 1940.