The Mier expedition was an unsuccessful military operation launched in November 1842 by a Texian militia against Mexican border settlements; it was related to the Somervell expedition. It included a major battle at Ciudad Mier on December 26 and 27, 1842, which the Mexicans won. The Texian attack was launched partly in hopes of financial gain and partly in retaliation for the Dawson Massacre (as named by Texans) earlier that year, in which thirty-six Texas militia were killed by the Mexican Army. Both conflicts were part of continuing efforts by each side to control the land between the Rio Grande and Nueces River. The Republic of Texas believed that the territory had been ceded to it in the Treaties of Velasco by which it gained independence, but Mexico did not agree.
