Texas faced ongoing conflicts with Mexico during this period. Mexico contested Texas' claim that the Rio Grande was its southern border. In 1841, Lamar sent 320 Texans on the Santa Fe Expedition to expand Texas' control, but they were captured by Mexican forces and imprisoned. In 1842, Mexican general Rafael Vasquez attacked several Texas towns in what became known as the Archives War. Later that year, 300 rebellious Texas troops invaded Mexico on the ill-fated Mier Expedition, where 100 Mexicans and 30 Texans were killed in battle and the Texan survivors were executed or imprisoned by Santa Anna's order.