On August 8, 1847, Buckner was appointed quartermaster of the 6th Infantry. Shortly thereafter, he participated in battles at San Antonio and Churubusco, being slightly wounded in the latter battle. He was appointed a brevet first lieutenant for gallantry at Churubusco and Contreras, but declined the honor in part because reports of his participation at Contreras were in error—he had been fighting in San Antonio at the time. Later, he was offered and accepted the same rank solely based on his conduct at Churubusco.