The leader who proclaimed the independence of the Republic of Texas was Sam Houston. In 1836, following the successful Battle of San Jacinto, Houston, who served as the commander-in-chief of the Texian Army, declared Texas's independence from Mexico. This declaration followed a series of conflicts, including the Battle of the Alamo, where Texian forces sought to separate from Mexican rule due to grievances over land, governance, and cultural differences. Houston later became the first president of the Republic of Texas, and he played a crucial role in its annexation by the United States in 1845, significantly impacting U.S. expansion.