He was born in Colonia del Sacramento in modern-day Uruguay, then part of the Viceroyalty of the Río de la Plata, on September 28, 1805, as the son of Juan Paunero Caballero, who settled there at the end of the 18th century, and Manuela Delgado Martínez, both of Spanish origin.

For a short time, he attended the Royal College of San Carlos in Buenos Aires, but the lack of materials meant that his family had no fortune which forced him to dedicate himself to earning a living, postponing his studies.

Paunero took Paz prisoner and defeated his army at the Battle of La Ciudadela under the orders of General Gregorio Aráoz de Lamadrid, he had to flee to Bolivia.

At the end of 1851 he enlisted as a colonel in the Colorado troops campaigning against federal governor Juan Manuel de Rosas and fought in the Battle of Caseros.

After a campaign of several months against the caudillo Ángel Vicente "El Chacho" Peñaloza, he signed a peace treaty, with pardon and amnesty for the defeated parties.

He remained a few more years in Córdoba, during which he actively participated in successive political conflicts and managed the installation or reinforcement of forts on the borders that existed at that time with the indigenous people.

He moved his troops to the southeast of the province, in a heroic march, and under the command of Venancio Flores he fought in the battle of Yatay and participated in the Siege of Uruguaiana.

The head of his vanguard, José Miguel Arredondo, attacked and defeated Saá at the Battle of San Ignacio, thus ending the civil war in Cuyo.

At the end of the Mitre government, he was appointed the Minister of War and Navy, and on the presidential elections of 1868 he was a vice-presidential candidate in the official formula headed by Rufino de Elizalde.

They were defeated by Sarmiento, who appointed him-among other reasons of state to alleviate his dire financial situation-Minister Plenipotentiary to the Empire of Brazil but died at Rio de Janeiro on June 7, 1871, at the age of 65.