As part of the famous Texas Brigade, the regiment fought at Eltham's Landing, Seven Pines, Gaines's Mill, Second Bull Run, South Mountain, Antietam, and Fredericksburg in 1862.

It fought at Suffolk, Gettysburg, Chickamauga and Wauhatchie in 1863 and the Wilderness, Spotsylvania, Cold Harbor, and the Siege of Petersburg in 1864.

In 1861, Governor Edward Clark set up a camp of instruction along the San Marcos River in Hays County.

At first, the term of enlistment was one year, but after the Battle of Fort Sumter on 12 April, the state authorities insisted that units must serve for the duration of the war.

John F. Marshall, editor of the Texas State Gazette, became lieutenant colonel and Bradfute Warwick, a Virginian, became major.

At this time, hundreds of the soldiers fell sick, which was a common occurrence in newly formed Civil War era military units.

[1] Army commander Joseph E. Johnston ordered the Texas Brigade to "feel the enemy gently and fall back".

Hood wished to prevent friendly fire accidents, so he ordered the troops to advance with unloaded weapons through thick woods.

Suddenly, the Texans stumbled onto an enemy patrol and a Union soldier raised his rifle to shoot Hood.

In the skirmish, Hood's brigade drove the Union soldiers back one mile and inflicted 186 casualties for the loss of only 48 Texans.

[7] The next day at 4:00 pm, Lee and James Longstreet mounted a major attack on the Union left flank.

[10] Nathan George Evans's brigade caught up with Hood's Texans, but their joint attack on McLean's Federals was repelled.

At the Battle of Antietam on 17 September the regiment suffered its worst losses of the war, losing 57 killed, 130 wounded, and 23 captured, a total of 210 casualties.

[14] At 7:00 am the following day, after the initial Union attack broke through the Confederate first line, the 2,300 men of Hood's division charged into the battle.

The 1st Texas rushed to the northern edge of the cornfield where it confronted a fresh Union battle line and was nearly destroyed.

The 4th Texas swung left to defend a fence line against Federals attacking from the west, and also suffered terrible losses.

[18] Soon after the attack started, Hood was badly wounded by a bursting shell, leaving his brigades to fight without his guiding hand.

But before the blunder could be fully exploited by the Texans and Alabamians, General Warren plugged the gap with the 140th New York Regiment and the Confederates were forced back again.

[21] The Texas Brigade transferred to the Western theater with Longstreet's corps where it fought at the Battle of Chickamauga on 19–20 September 1863.

Attempts to press farther were stopped by artillery and John T. Wilder's Union brigade armed with Spencer repeating rifles.

At this time, Law received intelligence that the overall operation failed; he ordered a retreat, but neglected to inform the 4th Texas.

Sergeant J. M. Polley wrote, "the officers and privates of the heretofore invincible 4th Texas stood not upon the order of their going, but ... stampeded and plunged into the shadowy depths behind them.

When General Lee tried to lead the counterattack, the Texas Brigade refused to advance until their army commander went to the rear.

[27] On 9 April 1865, the 4th Texas had only 15 officers and 143 men when Lee's army surrendered after the Battle of Appomattox Court House.