L. B. Franks was commander of the Texan artillery during the Siege of Bexar. On November 27, 1835, Gen. Edward Burleson, commander of the Texas forces, appointed Franks lieutenant colonel of the Texan artillery – comprising two cannons and fifteen gunners – and, due to the illness of James C. Neill, Franks served as artillery commander at the siege of Bexar, December 5–9, 1835. His one twelve-pounder, however, became unmounted, and the artillery did little effective service in the fight. Although fearful that the enemy had received a large-caliber mortar that would be damaging to the assaulting troops, Franks advised that the Texans not retreat but press home their attack on the Alamo. His irritation at Burleson’s aide-de-camp, Peter W. Grayson, for failing to forward reinforcements to the troops assaulting the Mexican fortifications caused him, on the third day of the battle, to send an intemperate note to Grayson, who thereupon withdrew from the army. Later that month Grayson and Franks met at San Felipe, and as a result of the meeting Franks published an apology to Grayson acknowledging that his note “was an unjust and wanton attack upon his feelings and character,” for which Franks asked Grayson’s pardon. The note, however, also drew the wrath of General Burleson, who, when Grayson was running for the presidency in 1838, attacked Franks as having held “a temporary but undeserved standing in the army.” Franks considered the attack mere “electioneering.”
On March 8, 1836, Franks wrote from the Nashville (Robertson) colony informing the convention at Washington-on-the-Brazos that he had formed a volunteer company of thirty men to take the field against Indian raiders on the northern frontier. With this force, mounted at his own expense, Franks pursued the raiders to the headwaters of the Little River. There he hoped to induce them to attack his force, which he disguised to resemble an immigrant wagon train. His letter was referred to the Committee on Indian Affairs. On April 23 George P. Digges reported to Sam Houston that he had organized two spy companies, one under Franks, which was to patrol between Robbins’ Ferry and Gonzales.