In February 1863, Col. Spruce McCoy Baird organized the Fourth Texas Cavalry, Arizona Brigade, which was composed primarily of men from New Mexico, Arizona, and California. Baird was a former United States attorney general of the New Mexico Territory. Other field officers of the Fourth Texas Cavalry were Maj. Edward Riordan and Lt. Col. Daniel Showalter. Baird's original recruiting efforts in late 1862 took place near Eagle Lake where John R. Baylor was also recruiting for another cavalry. Baird's recruiting efforts were not successful, so he relocated his recruiting efforts near the Pecos River, in far West Texas. His new recruits consisted of draft evaders, deserters, and other less desirable men who resided in the land between Confederate Texas and Union-held New Mexico. Lack of discipline was a major problem within the Fourth Texas Cavalry due to the quality of the recruits.
By late 1863, the Fourth Texas Cavalry took to the field as a mobile reserve force. The cavalry was divided into two battalions. One battalion was under the leadership of Lieutenant Colonel Showalter and ordered to Fort Washita, Cherokee Nation, in present-day Oklahoma. The second battalion was under the leadership of Colonel Baird and sent to Brazoria County on the Texas Gulf Coast. On December 15, 1863, Lieutenant Showalter's battalion was ordered to join Col. John Salmon Ford in San Antonio as a part of the Cavalry of the West. For unknown reasons, Lieutenant Showalter's battalion did not join Ford's command until March 31, 1864. Colonel Baird's battalion did join Ford in San Antonio. The Cavalry of the West fought against the Union forces under the command of Maj. Gen. Francis J. Herron and captured Brownsville in July 1864. Due to his disappointment of being placed under Colonel Ford's command at San Antonio, Colonel Baird turned the Fourth Cavalry over to Lieutenant Colonel Showalter.
Under the leadership of Lieutenant Colonel Showalter, the Fourth Cavalry was a major participant in the battles of Rancho Las Rinas and Rancho del Carmen. The Cavalry was praised for its capture of the USS Ark, a Union riverboat, on August 8, 1864. A short time later, praise turned to shame, as Lieutenant Colonel Showalter faced court martial for retreating before a raid by the Mexican bandit, Juan Cortina, at the first battle of Palmito Ranch in September 1864. It was reported that Showalter had a drinking problem and was drunk at this time. Colonel Ford defended Showalter's action stating he was a chivalrous brave man when not under the influence.
There are conflicting and scant records concerning the Fourth Cavalry's activities in 1865. In February 1865 the Fourth Cavalry was ordered to Houston but was apparently diverted to Corpus Christi en route. At this time records indicate a breakup of the Fourth Cavalry by the end of February. One record has Colonel Showalter and a portion of the Fourth Cavalry under the command of Colonel Ford near Palmito Ranch on the Rio Grande. Another record has a part of the Fourth Cavalry in Cooke County in northern Texas. This section of the Fourth Cavalry was accused of various acts of murder and theft that ended with other Confederate troops being ordered to hunt them down. With the fact that the regiment had once been divided into two battalions, it is possible that this could have occurred. Lieutenant Colonel Showalter is reported to have died in 1866, cause of death unknown.