Athanase de Mézières y Clugny, the son of Louis Christophe de Mézières and Marie Antoinette Clugny, was born to nobility in Paris and was baptized on March 26, 1719. His career as an infantryman in Louisiana began in the early 1730s. Over the next thirty years he served as ensign, lieutenant, and captain. In the 1740s he was assigned to the French outpost at Natchitoches, where in 1746 he married Marie Petronille Feliciane de St. Denis, the daughter of Louis Juchereau and Manuela Sánchez Navarro de St. Denis. This brief marriage ended when Marie died in childbirth in 1747, and Mézières later married Pelagie Fazende. On September 15, 1763, shortly after Louisiana had passed from French to Spanish control, he was discharged from the infantry. Like many Frenchmen in Louisiana, he offered his services to Spain, and in late 1769 Alejandro O'Reilly appointed him as lieutenant governor of Natchitoches. Mézières, skilled in Latin, French, and Spanish as well as in several Indian languages, embarked on an extraordinary career as Spanish agent to the Indians of northern Texas. In 1770 he carried out the first of several expeditions to the Red River, and in the following year he successfully negotiated treaties with the Kichais, Tawakonis, and Taovayas, and by their proxy, with the Tonkawas. In 1778 Bernardo de Gálvez, governor of Louisiana, released Mézières for additional services in Texas, where he was to forge an alliance among the Spanish, Comanches, and Norteños against the Apaches. To this end Mézières traveled extensively over the course of a year-to the new town of Bucareli, to the Red River, and even to New Orleans. En route between Los Adaes and Nacogdoches, he suffered a serious head injury when thrown from his horse. After convalescence, he continued on to San Antonio, where he arrived in September 1779. In the capital he learned of his appointment as governor of Texas. But Mézières, some sixty years of age, remained gravely ill and did not assume office. He had one child by his first wife and eight by his second. He died at San Antonio on November 2, 1779, having never fully recovered from being unhorsed, and the proposed general alliance with the Comanches and Norteños was never realized.