In July 1861 a force under Lieutenant-Colonel John R. Baylor arrived in El Paso, Texas across the border from Mesilla. With support from the secessionist residents of Mesilla Baylor's 2nd Texas Mounted Rifles entered the territory and took a position in the town on July 25. Union forces under Major Isaac Lynde at nearby Fort Fillmore prepared to attack Baylor. On July 25 the two armies met outside of town at the Battle of Mesilla in a brief engagement in which the Union troops were defeated.