The Castilla Real affair was a diplomatic incident in July of 1839 in the territory disputed between the nascent Republic of Texas and the Empire of Mexico. While out patrolling, a small group of Texian soldiers came upon a Mexican garrison at the fort of Castilla Real. Due to lingual barriers and confusion in the dark, a Mexican warning shot fired was viewed by the Texians as an attack, and they promptly fired back. One Mexican was killed, and in the ensuing Mexican volley two Texians were injured.