Mendoza was a member of the Royal Service of the Regimiento de Guardias de Infantería Española. In 1708, he became a lieutenant colonel of the infantry. He served as a soldier, Cabo de esquadra, and Sergeant. Mendoza fought in the War of the Spanish Succession of the early 18th century. He fought in the following battles: the Battle of La Gudina, the Battle of Zaragoza, the siege and advance on Viruega, the Battle of Villaviciosa, the sieges in the Spanish municipalities of Castellón, Cardona, Lerida and Tortosa, the Siege of Barcelona, the blockade of Olivenza, the capture of Balaguer, the detachment of Arenes, and the siege and capture of Estadilla. He also participated in the capture of Barcelona and all the operations involved in the campaign to Sardinia and Sicily, as well as in the capture of the Castillo de Palermo, the sieges and captures of Messina and Melazo, and the conquest and restoration of Oran. He also participated in the reunions held in the Spanish municipalities Almenara, Castellón and Peñalba. In 1735, Rodrigo was appointed Captain of armed forces and Ayudante mayor of the plaza of Ciudad Rodrigo in Spain.On 12 May 1737, King Philip IV of Spain appointed Mendoza Governor of New Mexico, although he did not occupy the government of the province until January 1739.
Mendoza embarked to the Viceroyalty of New Spain with his wife and children, plus a maid and three servants. Shortly after he arrived in the province of Santa Fe de Nuevo México in 1739 to become governor, a small party of Frenchmen visited Santa Fe pueblo. In 1741, Mendoza issued laws to protect and defend women and children in Taos. So issued a law to punish all men who wounded, killed or mistreating to "infidel" woman and boys, fining them with three-hundred silver pesos and six years in exile. However, this law was impossible to carry out, especially due to the distance between Santa Fe, and Taos. During Mendoza's administration, many children were captured, especially children who belonged to the Navajo, Utes, Comanche and Apache peoples. Later, a group of seven Comanches traveled to Taos Pueblo to trade tobacco and they explained to Mendoza that their people would visit the valley when the snows abandoned the mountains. However, they also said them the French had armed them with muskets and later traveled to some unknown direction beyond their lands. However, they indicated also that two French traders would go to visit New Mexico in the spring. When the news reached to Mendoza, he decided to establish a presidio in the north to protect the population of Taos from the possible French invasion, and did so in the Jicarilla Apache's abandoned settlement. The presidio would use many shelters that had been built in the place. Despite this, when the French traders visited Santa Fe, Mendoza accepted them and gave them a map showing the Spanish settlements in Santa Fe de Nuevo México. Later, the traders brought the map back to the French Louisiana colony in New France, where they were based, causing the repentance of Mendoza for having given them the map. The trade with the French traders allowed the Spanish obtain French guns. Mendoza was replaced by Joaquín Codallos y Rabal as colonial governor of Santa Fe de Nuevo México province in 1743.
Personal life
Mendoza married María Ferreras de la Torre. They had three children — Francisca Micaela, María Manuela and Hermenegildo. Having left the New Mexico office in 1743, Mendoza apparently lived in Santa Fe de Nuevo Mexico for a while. His daughter, Francisca Micaela, around 14 years old at that time, married the next governor of New Mexico, Joaquín Codallos y Rabal.
