A conflict between the USA and Mexico. Hostilities between the two countries began shortly after the USA annexed (1845) the Mexican state of Texas and sought to expand the boundaries of the state to include still more territory. In the ensuing war General Stephen Kearny took over the New Mexico territory and Captain John Frémont annexed the California territory almost without a fight. In northern Mexico stiffer opposition was encountered as General Zachary Taylor invaded Mexico across the Rio Grande and defeated General Antonio López de Santa Anna in the bloody Battle of Buena Vista (22–23 February 1847). The fiercest fighting occurred in central Mexico. General Winfield Scott’s order of a mortar bombardment of Vera Cruz resulted in the deaths of hundreds of civilians. The US army then moved inland to Mexico City, where hotly contested engagements were fought at Molino del Rey, and Chapultepec Hill (12–13 September 1847). The US capture of the capital city (1847) occasioned the Mexican surrender. The Treaty of Guadalupe Hidalgo (1848) ended hostilities. By the terms of the treaty the USA confirmed its claim to Texas and gained control of the area, which would later become the states of New Mexico, Arizona, and California (where gold had recently been discovered). The USA agreed to pay Mexico 15 million dollars in return.