The 18th Georgia briefly guarded prisoners in Richmond captured at the First Battle of Bull Run (Manassas) and served garrison duty for two weeks in Goldsboro, North Carolina.

[citation needed] For the next year they would be an integral member of the Texas Brigade as it fought from the Peninsula Campaign (May - July 1862) to Antietam.

Battle of Second Manassas) where members captured two stands of colors (those of the 24th and 10th New York Infantry regiments),[citation needed] and where, along with the Texas Brigade, they spearheaded General Longstreet's assault on Union General John Pope's left, nearly wiping out the 5th New York Zouaves and captured a battery of four guns.

In the ensuing Battle of Fredericksburg, the regiment fought behind the stone wall on Marye's Heights sustaining losses of 14 killed and 30 wounded while inflicting heavy casualties upon the enemy.

Jackson's Corps, with McLaws' Division on the left flank, remained on the Fredericksburg front until the night of May 1.

Around Gettysburg, on the second day of battle after taking the city, Lee ordered Longstreet's Corps to attack diagonally from Little Round Top northward.

The Confederate attack, coming late in the afternoon, saw Longstreet capture the positions west of Little Round Top known as Peach Orchard, Wheat Field, and Devil's Den on the Federal left.

In September 1863, Longstreet's Corps left the Army of Northern Virginia by rail to join the Battle of Chickamauga in northwest Georgia, near Dalton.

By December 12, 1863, his forces arrived at Rogersville, and on the 15th he attempted to capture three brigades of Federal cavalry at the Battle of Bean's Station.

On May 5, 1864, Gen. Longstreet's Corps was hit by the Federals on Old Turnpike and Orange Plank Road in the Battle of the Wilderness.

Then, at the Battle of Cold Harbor (May 31 - June 12), northeast of Richmond, Grant launched several very heavy attacks against Lee's army, including the 18th Georgia Regiment.

August 7, 1864, the unit was reassigned to operations against Sheridan's Campaign in the Shenandoah Valley where the 18th Georgia saw many small battles.

And lastly, on October 19, 1864, the unit saw action in the Battle of Cedar Creek, Middletown, and Belle Grove, Virginia.

Finally, on April 8, 1865 the 18th Georgia Regiment, assigned to Gen. Kershaw's Division, Gen. Longstreet's First Corps, Army of Northern Virginia was represented at the surrender of Confederate Forces at Appomattox Court House by less than 60 members, the highest ranking of which was one Lieutenant Gideon J. Lasseter.