Joaquín de Arredondo was the most powerful and influential person in northeastern New Spain from 1811 to 1821. His rise to prominence began in 1811 when the Spanish military officer and a small royalist army suppressed Miguel Hidalgo’s revolution in the province of Nuevo Santander. This prompted the Spanish government to promote Arredondo to Commandant General of the Eastern Internal Provinces, making him the foremost civil and military authority in northeastern New Spain. Arredondo’s tenure as commandant general proved difficult, as he had to deal with insurgents, invaders from the United States, hostile Indians, pirates, and smugglers. Because warfare in Europe siphoned much needed military and financial support, and disagreements with New Spain’s leadership resulted in reductions of the commandant general’s authority, Arredondo confronted these threats with little assistance from the Spanish government. In spite of these obstacles, he maintained royalist control of New Spain from 1811 to 1821, and, in doing so, changed the course of Texas, Mexican, and United States history. In 1813, he defeated insurgents and American invaders at the Battle of Medina, and from 1817 to 1820, his forces stopped Xavier Mina’s attempt to bring independence to New Spain, prevented French exiles from establishing a colony in Texas, and defeated James Long’s filibustering expedition from the United States. Although unable to sustain Spanish rule in 1821, Arredondo’s approval of Moses Austin’s petition to settle families from the United States in Texas in 1820 and his role in the development of Antonio López de Santa Anna, meant the officer continued to influence Mexico. Perhaps Arredondo’s greatest importance is that the study of his life provides a means to learn about an internationally contested region during one of the most turbulent eras in North American history.