answers: the Nueces River
context: border with Texas. On April 25, 1846, a 2,000-strong Mexican cavalry detachment attacked a 70-man U.S. patrol that had been sent into the contested territory north of the Rio Grande and south of the Nueces River. The Mexican cavalry routed the patrol, killing 16 U.S. soldiers in what later became known as the Thornton Affair. Both nations declared war. In the ensuing Mexican–American War, there were no more battles fought in Texas, but it became a major staging point for the American invasion of northern Mexico. One of the primary motivations for annexation was the Texas government's huge debts. The </s> clearly defined and remained so until the Mexican colony became independent from Spain and entered a period of political instability. Mexico attempted to create a buffer zone at the border that would prevent possible invasion from the North. The Mexican government encouraged thousands of their own citizens to settle in the region that is now known as Texas and even offered inexpensive land to settlers from the United States in exchange for populating the area. The influx of people did not provide the defense that Mexico had hoped for and instead Texas declared its independence in 1836, which lasted until </s> Mexican–American War. The first battles of the war were fought in Texas: the Siege of Fort Texas, Battle of Palo Alto and Battle of Resaca de la Palma. After these decisive victories, the United States invaded Mexican territory ending the fighting in Texas. After a series of United States victories, the Treaty of Guadalupe Hidalgo ended the two-year war. In return, for US$18,250,000, Mexico gave the U.S. undisputed control of Texas, ceded the Mexican Cession in 1848, most of which today is called the American Southwest, and Texas's borders were established at the Rio Grande. The Compromise of 1850 set
question: river that mexico claimed was the texas border