In 1853 Mr. Pettus was appointed by Governor Collier to fill a vacancy in the district solicitorship. Characteristically fair and just, he won great favor and popularity throughout west Alabama, so that when he offered for the judgeship of the circuit, in 1855, he was easily elected. This position he surrendered in 1858, in order to remove to Cahaba, then a thriving center of wealth and intelligence, where he practiced law till the opening of the war. During the early part of the year 1861, troops were rapidly raised and organized into regiments, and as rapidly as possible, sent to the front. In co-operation with Colonel Garratt of Perry County, Pettus raised a regiment of infantry, which became the Twentieth Alabama, of which regiment he became the major, and somewhat later was made the lieutenant colonel of the command. Assigned to duty in the western army, the regiment did not long remain inactive. Colonel Pettus won laurels by leading the army of General E. Kirby Smith in driving the enemy into Covington and Cincinnati. His regiment was afterward ordered to Mississippi and Colonel Pettus was engaged in the battles of Port Gibson and Baker's Creek. He was captured at Port Gibson, but succeeded in effecting his escape and in rejoining his command. On the occasion of the promotion of Colonel Garratt at Vicksburg Pettus became the colonel of the regiment. A notable incident in connection with the siege of Vicksburg gave to Colonel Pettus fame for leadership, and for unquestioned courage throughout the army. At an important point in the works the enemy had captured a valuable redoubt, and General Stephen D. Lee was anxious to have it retaken. The undertaking was full of peril, and the success of the undertaking was doubtful. To perform the perilous undertaking, Colonel Pettus volunteered to the commanding officer his services. Neither his own regiment nor any of the others were willing to be led into so perilous an undertaking, but Waul's Texas Legion volunteered in a body to make the hazardous attack. So formidable was the redoubt that the enemy supposed himself secure from attack. Taking advantage of this condition, Colonel Pettus, at the head of the brave Texans, dashed unawares on the enemy, threw the forces into utter confusion, and retook the redoubt, together with one hundred prisoners and three flags. Thirty big guns were at once trained on the point, but Colonel Pettus bore away his spoils without the loss of a man.