He served under the leaders Javier López and Gregorio Aráoz de Lamadrid He participated in the Battle of El Tala at the front of the reserve, and was appointed to the rank of colonel in November 1826.

He fought in the army of the governor of Tucumán, Javier López, in the Battle of La Tablada against Facundo Quiroga, and in the subsequent campaign in Catamarca Province.

The federal governor Alejandro Heredia took his father, Juan Bautista Paz, as its general minister, and he obtained a pardon for his son.

By 1835, after outstanding performance in the combat of Famaillá in January 1836, when former Governor Javier Lopez was finally defeated, he earned the post of commander of the forces of Tucumán.

In April 1837 he was sent to the governor of Buenos Aires, Juan Manuel de Rosas, by the governments of Tucumán, Catamarca, Salta and Jujuy, to arrange support for the External Relations Minister of the Argentina Confederation for the war against the Peru-Bolivian Confederacy.

Moving to Orán, he led a campaign from there to Tarija, where he obtained from the military commander of that place, Ildefonso Cuellar, a ruling against General Andrés de Santa Cruz.

On August 22, Heredia ordered the withdrawal of his army, leaving continuation of the war to the forces of Chile, which eventually defeated Santa Cruz.

He was the chief of staff of the army, and directed operations against the reactionary forces led by Colonel Pedro Rosas y Belgrano.

During the two years following, he inspected the military forces of the southern Confederacy and submitted an extensive report to President Justo José de Urquiza.