The Mexican state of Tejas was wrested from Mexico by Anglo-American immigrants who became Mexican citizens but refused to honor the oaths they swore as grantees of Mexican land. A new centralist regime for Mexico led the Anglo Texians to mount and win the Texas Revolution in 1835-1836. The resultant Republic of Texas boasted of its sovereignty for a decade, then became a state in the United States of America—the fifteenth slave state—in December 1845. The divisive issues of slavery and the southern boundary of Texas, when enlarged by the overarching motivation of “Manifest Destiny,” sparked the Mexican-American War in May 1846. Fifteen years after becoming a state, Texas seceded from the Union in 1861, and joined the Confederate States of America. Texas was readmitted to the United States in 1870.