<P> The First Battle of Mesilla, was fought on July 25, 1861 at Mesilla in New Mexico Territory, in present - day Doña Ana County, New Mexico . </P> <P> It was an engagement between Confederate and Union forces during the American Civil War . The battle resulted in a Confederate victory and led directly to the official establishing of a Confederate Arizona Territory, consisting of the southern portion of the New Mexico Territory . The victory paved the way for the Confederate New Mexico Campaign the following year . </P> <P> Following the secession of Texas in February 1861 and its joining the Confederacy, a battalion of the 2nd Texas Mounted Rifles under Lieutenant Colonel John R. Baylor was sent to occupy the series of forts along the western Texas frontier which had been abandoned by the Union Army . Baylor's orders from the Department of Texas commander, Colonel Earl Van Dorn, allowed him to advance into New Mexico in order to attack the Union forts along the Rio Grande if he thought the situation called for such measures . Convinced that the Union force at Fort Fillmore would soon attack, Baylor decided to take the initiative and launch an attack of his own . </P> <P> Leaving during the night of July 23, Baylor arrived in Mesilla the next night, preparing to launch a surprise attack the next morning . However, a Confederate deserter informed the fort's commander, Major Isaac Lynde, of the plans . The next day, Baylor led his battalion across the Rio Grande into Mesilla, to the cheers of the population . A company of Arizona Confederates joined Baylor here, and were convinced to muster into the Confederate Army . </P>

Who led the confederate force that captured fort fillmore