The alliance between the Wichita, especially the Taovayas, and the Comanche began to break up in the 1770s as the Wichita sought a better relationship with the Spanish. Taovaya power in Texas declined sharply after an epidemic, probably smallpox, in 1777 and 1778 killed about one-third of the tribe. After the Americans took over their territory as a result of the Louisiana Purchase in 1803 and the independence of Texas in 1836, all the related tribes were increasingly lumped together and dubbed "Wichita." That designation also included the Kichai of northern Texas, who spoke a different although a related language.