War with Mexico A Chronology of the U.S.-Mexican War Battles, Skirmishes & Other Important Events 1846 25 April 1846: Thornton Affair, South Texas 3-9 May 1846: Siege of Fort Texas (Fort Brown), South Texas 8 May 1846: Battle of Palo Alto, South Texas May 9, 1846: Battle of Resaca de la Palma, South Texas 13 May 1846: U.S. declares war against Mexico. 18 May 1846: U.S. troops occupy Matamoros. 7 July 1846: U.S. Naval forces occupy Monterey, California. 14 July 1846: U.S. forces occupy Camargo. 21 July 1846: General Taylor issues orders for the discharge of 3 and 6 month volunteers. 30 July 1846: General Taylor issues orders for movement of troops to Camargo. 16 August 1846: Santa Anna returns to Mexico from exile in Cuba. 18 August 1846: U.S. forces under General Stephen W. Kearny occupy Santa Fé, New Mexico. 19 August 1846: First U.S. troops depart Camargo for Monterey, Mexico. 20-24 Sept. 1846: Battle of Monterey, Northern Mexico 7 Oct. 7 1846: Battle of Dominguez Rancho, Southern California. 14 Nov. 1846: U.S. Navy seizes Tampico. 16 Nov. 1846: U.S. forces occupy Saltillo. Battle of Natividad, Northern California. 6 Dec. 1846: Battle of San Pasqual, California. 25 Dec. 1846: Battle of El Brazito, New Mexico. 1847 2 January 1847: Battle of Santa Clara, California. 8 January 1847: Battle of Rio San Gabriel (Los Angeles), California. 9 January 1847: Battle of La Mesa (Los Angeles), California. 24 January 1847: Battles of Cañada and Mora, New Mexico. 29 January 1847: Battle of Embudo Pass, New Mexico. 3-4 February 1847: Battle of Pueblo de Taos, New Mexico. 22-23 February 1847: Battle of Buena Vista. 28 Feb. 1847: Battle of the Sacramento, Northern Mexico 9 March 1847: 10,000 U.S. troops landed on beaches by Navy at Vera Cruz. 9-29 March 1847: Siege and bombardment of Vera Cruz. 29 March 1847: Mexican forces at Vera Cruz capitulate. 18 April 1847: Battle of Cerro Gordo. 6 June 1847: Affair at Las Vegas, New Mexico. 19-20 August 1847: Battles of Contreras and Churubusco. 8 Sept. 1847: Battle of Molino Del Rey. 13 Sept. 1847: Battle of Chapultepec. 13-14 Sept. 1847: Battle for Mexico City. 14 Sept. - 12 Oct. 1847: Siege of Puebla. 15 Sept. 1847: U.S. forces under General Winfield Scott occupy Mexico City. 1848 2 February 1848: Treaty of Guadalupe Hidalgo signed, formally ending the war. 10 March 1848: U.S. Senate ratifies Treaty of Guadalupe Hidalgo, with amendments. March 1848: Santa Anna departs Mexico for exile in Jamaica. 25 May 1848: Mexican Congress ratifies Treaty of Guadalupe Hidalgo. 4 July 1848: President Polk formally announces ratification of Treaty of Guadalupe Hidalgo. 2 August 1848: Last U.S troops leave Mexico. .