He became a citizen of Mexico on February 11, 1835, applied for a headright in David G. Burnet's colony, and sent for his family. After hearing Nacogdoches citizens denounce the despotism of Mexico, Rusk became involved in the independence movement. He organized volunteers from Nacogdoches and hastened to Gonzales, where his men joined Stephen F. Austin's army in preventing the Mexicans from seizing their cannon. They proceeded to San Antonio, but Rusk left the army before the siege of Bexar. The provisional government named him inspector general of the army in the Nacogdoches District, a position he filled from December 14, 1835, to February 26, 1836. As a delegate from Nacogdoches to the Convention of 1836, Rusk not only signed the Texas Declaration of Independence but also chaired the committee to revise the constitution. The ad interim government, installed on March 17, 1836, appointed Rusk Secretary of War.
When informed that the Alamo had fallen and the Mexicans were moving eastward, Rusk helped President Burnet to move the government to Harrisburg. Rusk ordered all the coastal communities to organize militias. After the Mexicans massacred James W. Fannin's army Burnet sent Rusk with orders for Gen. Sam Houston to make a stand against the enemy, and upon learning that Antonio López de Santa Anna intended to capture the government at Harrisburg the Texas army marched to Buffalo Bayou. As a security measure, Houston and Rusk remained silent about their plans. Rusk participated with bravery in the defeat of Santa Anna on April 21, 1836, in the battle of San Jacinto. From May 4 to October 31, 1836, he served as commander in chief of the Army of the Republic of Texas, with the rank of brigadier general. He followed the Mexican troops westward as they retired from Texas to be certain of their retreat beyond the Rio Grande. Then he conducted a military funeral for the troops massacred at Goliad. When it appeared that the Mexicans intended to attack Texas from Matamoros, Rusk called for more troops. Though he had 2,500 soldiers by July, he maintained a defensive position.
In the first regularly elected administration, President Houston appointed Rusk Secretary of War, but after a few weeks he resigned to take care of pressing domestic problems. At the insistence of friends, however, he represented Nacogdoches in the Second Congress of the republic, from September 25, 1837, to May 24, 1838. While in the capital, Houston, he taught a Christian Sunday school class. Like many prominent Texans, Rusk became a Mason. He joined Milam Lodge No. 40 in Nacogdoches in 1837 and was a founding member of the Grand Lodge of Texas, organized in Houston on December 20, 1837. In the election of 1838 and in succeeding ones, friends importuned Rusk to be a presidential candidate, but he refused. As chairman of the House Military Committee in 1837, he sponsored a militia bill that passed over Houston's veto, and Congress elected Rusk major general of the militia.
In the summer of 1838 he commanded the Nacogdoches militia, which suppressed the Córdova Rebellion. Rusk suspected Cherokee involvement in the rebellion, but Chief Bowl emphatically denied any collusion with Córdova. In October, when Mexican agents were discovered among the Kickapoo Indians, Rusk defeated those Indians and their Indian allies. He captured marauding Caddo Indians in November 1838, and he risked an international incident when he invaded United States territory to return them to the Indian agent in Shreveport. Unrest among the Cherokees grew after the failure to ratify the Cherokee Treaty of 1836, which would have given the Cherokees title to the lands they occupied in East Texas. In July 1839 the final battle with the Cherokees and their allies was fought. Papers taken from captured Mexican agents implicated the Cherokees in a Mexican-Indian conspiracy against the Republic of Texas. Because he agreed with President Mirabeau B. Lamar's determination to remove the Cherokees, Rusk commanded part of the troops in the battle of the Neches, in which the Cherokees were driven into Oklahoma.
On December 12, 1838, Congress elected Rusk chief justice of the Supreme Court. He recognized that he was working in a system that combined Spanish and English law and practices, systems that did not always coincide. In Milam County v. Bell he established the rule of mandamus against public officers. He served until June 30, 1840, when he resigned to resume his law practice. Later he headed the bar of the Republic of Texas. He and J. Pinckney Henderson, later the first governor of the state of Texas, formed a law partnership on February 25, 1841, the most famous law firm in Texas of that day. For a short time the firm also included Kenneth L. Anderson, later vice president under Anson Jones. One of the most widely known cases Rusk handled was the murder of Robert Potter, former Secretary of the Texas Navy, in 1842. Rusk represented the ten defendants, secured their bail, which had previously been denied, and obtained a dismissal before the case was to be tried on May 6, 1843. Earlier in 1843 Rusk had been called once again to serve as a military commander. Concern over the lack of protection on the frontier caused Congress, in a joint ballot on January 16, 1843, to elect Rusk major general of the militia of the Republic of Texas. But he resigned in June when Houston obstructed his plans for aggressive warfare against Mexico. Rusk then turned his energies to establishing Nacogdoches University. He was vice president of the university when the charter was granted in 1845 and president in 1846.
The annexation of Texas by the United States was heartily supported by Rusk. He was president of the Convention of 1845, which accepted the annexation terms. Rusk's legal knowledge contributed significantly to the constitution of the new state. The first state legislature elected him and Houston to the United States Senate in February 1846. Rusk received the larger number of votes and the longer term of office. The two men forgot past differences as they worked to settle the southwest boundary question in favor of the Texas claim to the Rio Grande. Rusk supported the position of President James K. Polk on the necessity of the Mexican War and the acquisition of California. In the debate over the Compromise of 1850, Rusk refused to endorse secession, proposed by some in the caucus of southern congressmen. He vigorously defended Texas claims to New Mexico and argued forcefully for just financial compensation for both the loss of revenue from import duties as well as the loss of territory. As chairman of the Committee of Post Offices and Post Roads, he sponsored bills that improved services and lowered postage rates. As an early advocate of a transcontinental railroad through Texas, he made speeches in the Senate and throughout Texas in support of a southern route and toured Texas in 1853 to investigate a possible route. The Gadsden Treaty received his support since it provided an easier railroad route to the Pacific. Rusk received the approval of the state legislature for his vote in favor of the Kansas-Nebraska Act. He was a popular man in his party and was encouraged to become a presidential candidate in 1856. President James Buchanan offered him the position of postmaster general in 1857. During the special session of March 1857 the United States Senate elected him president pro tem.
While Rusk attended the spring session of Congress, Mrs. Rusk succumbed to tuberculosis, on April 23, 1856. Five of their seven children were still living at the time. Despondent over the death of his wife and ill from a tumor at the base of his neck, Rusk committed suicide on July 29, 1857. The State of Texas placed a monument at the graves of Rusk and his wife in Oak Grove Cemetery, Nacogdoches. Rusk County and the town of Rusk were named in his honor.
31° 36.165, -094° 38.979
Oak Grove Cemetery