First Battle of Mesilla The First Battle of Mesilla , fought on July 25 , 1861 at Mesilla in what is now New Mexico , 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 . Background . 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 . 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 . On July 25 , leaving a small force behind to guard the fort , Lynde led 380 Regulars to the village to drive out Baylor . Battle . Lynde approached the town with his command and demanded Baylor ' s surrender . When Baylor refused , Lynde deployed his men into a skirmish line and opened fire with his mountain howitzers . The infantry was ordered to advance but heavy sand and corn fields interfered with this attack . Lynde then ordered his cavalry , three companies of the Regiment of Mounted Rifles , to charge Baylor ' s men . The Confederates managed to shoot many of the Union soldiers during this time , which disorganized the attack . The Union assault was repulsed , and both sides began skirmishing at long range . Lynde reformed his command but decided to retreat back to the fort , with the Confederates troops and armed Arizona citizens in pursuit . Lynde lost a disputed three to thirteen men killed and two officers and four men wounded , while Baylor lost a disputed two dead and seven seriously wounded with twenty horses killed . Aftermath . At sunset the next day , Baylor ordered his artillery and more cavalry to reinforce him , while the rest of his command moved into position to attack the fort the next day . During the same night , the Confederates managed to capture 85 of the fort ' s horses , which formed most of the fort ' s transportation . Fearing an attack the next day , Lynde abandoned Fort Fillmore after destroying the ammunition and supplies in the citadel . He retreated northeast towards Fort Stanton across the dry Organ Mountains . Many Union troops apparently had filled their canteens with the fort ' s medicinal whiskey instead of water , hardly wise for a summertime march across desert country . During the pursuit the following day , the Confederates were able to capture dozens of straggling Federals . Lynde ' s dehydrated command , reduced to 100 men by this time , was overtaken by the Confederates and forced to surrender at San Agustine Springs on July 27 . The prisoners were paroled , and Baylor concentrated his battalion at the fort . He was able to refit his command with the captured Springfield rifles and other captured equipment . The Confederate victory at Mesilla actualized local overtures towards secession , which had been ratified by two conventions in March 1861 . On August 1 Baylor declared the establishment of an organized Confederate Arizona Territory , consisting of the portion of the New Mexico Territory south of the 34th parallel north . Baylor installed himself as the new territory ' s military governor , and declared martial law . Baylor ' s success at Mesilla led to Henry Hopkins Sibley ' s ambitious New Mexico Campaign the following February . The Second Battle of Mesilla was a skirmish fought in the desert near Mesilla on June 1 , 1862 between Arizona rebels and New Mexican militia . The engagement ended with a Union victory and prompted the rebels to withdraw from Mesilla a few days later on June 7 . On 25 November 1861 Major Lynde was , by direction of the President of the United States , dropped from the Army rolls for " " abandoning his post — Fort Fillmore , N . Mex . — on the 27th of July , 1861 , and subsequently surrendering his command to an inferior force of insurgents " " .