The U.S.-Mexican War, also known as the Mexican-American War and the Mexican War, took place from 1846 to 1848, and was mainly about control of Texas. Mexico claimed this territory despite Texas having declared itself a republic years earlier, while the U.S. wished to annex Texas and make it the 28th state. The war was fought with no allies and was the first offensive war for the United States.

This chronology focuses on the military actions of the war as well as the many Indian incursions before the war. The various campaigns, sieges and skirmishes in both the United States and Mexico, on both land and sea, are covered. Some of the heroes of this war also served in the War of 1812 and many rose to high military office during the Civil War. The contributions of the individuals who later became generals during the Civil War are also highlighted here.