The Fifth Texas Cavalry was also known as the Fifth Texas Mounted Rifles and the Fifth Texas Mounted Volunteers. On August 12, 1861, Confederate Brig. Gen. Henry H. Sibley arrived in San Antonio to organize a brigade for a campaign in New Mexico and Arizona. His ultimate goal was to capture the gold and silver mines of Colorado and California and to secure a Confederate pathway to the Pacific. Three regiments of cavalry or mounted riflemen, each with an attached battery of howitzers, were quickly formed for service in what would come to be known as the Sibley's Brigade: the Fourth Texas under Col. James Reily, the Seventh Texas under Col. William Steele, and the Fifth Texas Mounted Volunteers. The Fifth was recruited, for the most part, in Waco, San Antonio, Bonham, Weatherford, and Austin and was organized and mustered into Confederate service at San Antonio with 926 officers and men. The volunteers supplied their horses and their own weapons, the quality of which varied widely. The regiment was to be commanded by the famed Texas Ranger, Thomas Green, who accepted his commission as colonel on August 20, 1861. Henry C. McNeill was elected as the regiment's lieutenant colonel and Samuel A. Lockridge as its major.
The Fifth Texas Mounted Rifles—numbering 835 effectives by the time it left San Antonio—marched for Fort Bliss in October. There Sibley took command of what would be designated as the Army of New Mexico. From Fort Bliss the all-Texas brigade began its march up the Rio Grande toward Santa Fe. After occupying Fort Thorn, New Mexico Territory, the brigade attempted the capture of Fort Craig. Although the fort remained in Union hands, the Texans defeated a sortie attempted by the garrison on February 20–21 at the battle of Valverde. The Fifth Texas Cavalry played a conspicuous role in the Confederate victory. With General Sibley indisposed, Colonel Green commanded the troops on the field. Capt. Willis L. Lang, the commander of Company B, led what was perhaps the only charge of lancers in the Civil War. As might have been expected, the company was cut to pieces, and its captain received an apparently mortal wound. (Despondent and in great pain, Lang later committed suicide.) The company's first lieutenant, Demetrius M. Bass, died of seven wounds received in the charge. Major Lockridge was also killed in action at Valverde, just at the point of overrunning a battery of four Union guns, and the regiment's adjutant, First Lt. Joseph D. Sayers, who Green compared to "a hero of the days of chivalry," was promoted to captain and transferred to command of the captured guns, afterward known as the Val Verde Battery.
The regiment also played a conspicuous part in subsequent engagements of the New Mexico campaign, notably Apache Canyon (March 26), Glorieta (March 28), and Peralta (April 14). After enduring a hideous march back to Texas when Sibley's campaign ended in failure after the destruction of the brigade's supplies at Glorieta, the Fifth Texas returned to San Antonio with only 454 officers and men fit for duty. During the campaign, 45 of the regiment's soldiers had been killed in action or mortally wounded, 31 died of disease, 81 had been wounded, and 209 had been taken prisoner. Tom Green, who had been the brigade's de facto commander throughout the New Mexico campaign, was promoted to brigadier general and given command of what had been the Sibley's Brigade, and Henry C. McNeill became the regiment's colonel. Hugh A. McPhaill, formerly the captain of Company E, who had replaced Lockridge as major, was promoted to lieutenant colonel, and John Samuel "Shrop" Shropshire, formerly the captain of Company A, became the regiment's new major. When Shropshire was killed in action at Glorieta, Denman W. Shannon, formerly the commander of Company C, was elected to replace him.
After a brief period in which the men rested and re-equipped themselves, the regiment was sent to the Texas Gulf Coast to take part in Maj. Gen. John B. Magruder's recapture of Galveston on January 1, 1863 (see GALVESTON, BATTLE OF). Confederate authorities at Houston refitted two steamboats lying in Buffalo Bayou into gunboats, armored with cotton bales. These were manned by volunteers from Green's command, humorously dubbed "horse marines."
From Galveston, the Fifth Texas Cavalry, as a part of Green's brigade, was transferred to the Bayou Teche region of southern Louisiana to resist Maj. Gen. Nathaniel P. Banks's attempted overland drive on Texas from the Mississippi River. The regiment fought with distinction through the spring of 1863 at the battles of Fort Bisland (April 12–13), Brashear City (June 23), and Donaldsonville, (June 28) where Major Shannon was wounded and captured and Capt. Daniel H. Ragsdale of Company D and lieutenants James A. Darby of Company I and James F. Cole of Company K of the Fifth were killed in action. (Following his exchange, Shannon returned to the regiment as its lieutenant colonel.) After his attempt to storm Donaldsonville was repulsed, General Green crossed the Atchafalaya River and on September 29 attacked the Union garrison at Fordoche. In this fight, also known as Stirling's Plantation, Green's command captured 462 prisoners and a battery of artillery. In the final battle of the campaign, Green won a significant victory over Maj. Gen. William B. Franklin's rear guard at Bayou Bourbeau on November 3, 1863.
During this campaign, Tom Green was promoted to major general and given command of the cavalry division of the Trans-Mississippi Department. His former brigade was assigned to Brig. Gen. Arthur Pendleton Bagby, who commanded it through the Red River campaign. Green's cavalry regiments, including the Fifth, returned to Texas during the winter of 1863–64, but with the opening of the Red River campaign in the spring of 1864 they returned to Louisiana to reinforce the Confederate Army of Maj. Gen. Richard Taylor.
The Fifth Texas Cavalry was heavily engaged throughout the entire campaign, especially at the battles of Mansfield (April 8, 1864) and Pleasant Hill (April 9, 1864). It was instrumental in harassing Maj. Gen. Nathaniel P. Banks's defeated Union Army on its retreat to Alexandria but received a severe check at the skirmish at Blair's Landing, Louisiana, where General Green was killed on April 12, 1864.
Following Banks's return to New Orleans, the Fifth Texas Cavalry was redeployed, first to the Teche region, then briefly to Valdalia, Louisiana, on the Mississippi River, then to Arkansas, and finally to Texas as part of Maj. Gen. John A. Wharton's division. In the final months of the war the brigade was commanded by acting Brig. Gen. Xavier B. Debray and then by Brig. Gen. William P. (Gotch) Hardeman. The Fifth Texas Cavalry spontaneously disbanded at Huntsville before Lt. Gen. Edmund Kirby Smith surrendered the Confederate forces in the Trans-Mississippi Department in June 1865.