The Callahan Expedition occurred in October 1855, when James Hughes Callahan led a force of 111 men into Mexico near Piedras Negras, Coahuila. The announced purpose of the unauthorized invasion was to punish Lipan Apache Indians who reportedly had raided along the Texas frontier during the summer and fall of 1855, then returned to Mexico, where they were protected by the authorities. In fact, the expedition likely was an attempt by Texas slaveholders to regain fugitive slaves who had fled to northern Mexico and to prevent Mexican authorities from permitting runaway slaves to settle in their midst. On July 5, 1855, Governor Elisha M. Pease authorized Callahan to organize a force to punish marauding Indians, who reportedly had increased their raids that summer when 3,000 United States troops were moved from the Texas frontier to Kansas. Callahan mustered his force into service on July 20. As Texas citizens continued to appeal to Pease for defense against the Indian raids, Callahan and his men left Bandera Pass on September 18 headed for the Rio Grande.
Texas slaveowners, meanwhile, had developed plans to capture fugitive slaves who had taken up refuge in northern Mexico, especially near San Fernando, Coahuila. Newspaper editor John S. (Rip) Ford estimated that more than 4,000 slaves had run away from Texas by 1855. That summer the slaveowners sent an emissary to talk with Governor Santiago Vidaurri of Nuevo León y Coahuila, but Vidaurri rebuffed the offer and warned his military commanders on the frontier to be ready for an invasion. The slaveowners apparently contacted Callahan and persuaded him to use his force to chastise the Mexicans as well as Indians, and perhaps to capture fugitive slaves. Callahan, at least, attempted to keep the real goal of his expedition secret, even from his own men. On August 31 he wrote his quartermaster, Edward Burleson, Jr., "I am bound to go to the Rio Grand if nothing hapens....I believe some of the boys have found out about the arrangement so I wrote to you as though my intention was to go to the uper country... to keep the matter as much of a secret as possible." Callahan crossed the swollen Rio Grande on October 1–3. Marching westward on October 3, the Texans encountered a Mexican detachment at the Río Escondido, about twenty-two miles from Piedras Negras. In the skirmish that followed, the Mexicans under Col. Emilio (Edvard Emil) Langberg reported a loss of four dead and three wounded, and Callahan reported four killed and seven wounded. The next morning, Callahan retreated to Piedras Negras and took possession of the town. As the Mexican force approached the town on October 5, Callahan ordered his men to set fire to houses to cover their retreat, and on the evening of October 6 Maj. Sidney Burbank, commander of the American forces across the river at Fort Duncan, turned four cannons to cover the Texans as they recrossed the river.
Callahan immediately defended his invasion of Mexico, claiming that he had received permission from the Mexican authorities to cross the river in pursuit of the Lipans. Pease defended Callahan's burning of Piedras Negras, saying that it was justified because the Mexicans had deceived Callahan by leading him into an ambush. Quartermaster Burleson alluded to a different purpose, however, when he wrote on November 11 to editor Ford about a slave who had escaped to Piedras Negras: The "Mexicans took him up and sent him back to this side immediately. We can guess why they did it." Historians have argued for years over the purpose of the expedition, but there was little misunderstanding at the time by those who were there. Even Bvt. Maj. Gen. Persifor F. Smith, who had encouraged Pease to appoint a company of rangers to help defend the frontier, reported to the adjutant general's office that the Texans were organizing a party to retrieve runaway slaves; "I presume," Smith wrote, "that the party of Captain Callahan was the one alluded to." The claims originating with this invasion of Mexico were not officially settled until 1876, when the Claims Commission of 1868 finished its work. The commission awarded approximately 150 Mexican citizens a total of $50,000 in damages.