Mexican–American War: The first large-scale amphibious assault in U.S. history is launched in the Siege of Veracruz.

The Mexican–American War, also known in the United States as the Mexican War, was an invasion of Mexico by the United States Army. It followed the 1845 American annexation of Texas, which Mexico still considered its territory because it refused to recognize the Treaties of Velasco, signed by President Antonio López de Santa Anna after he was captured by the Texian Army during the 1836 Texas Revolution. The Republic of Texas was de facto an independent country, but most of its Anglo-American citizens who had moved from the United States to Texas after 1822 wanted to be annexed by the United States.

Amphibious warfare is a type of offensive military operation that today uses naval ships to project ground and air power onto a hostile or potentially hostile shore at a designated landing beach. Through history the operations were conducted using ship's boats as the primary method of delivering troops to shore. Since the Gallipoli Campaign, specialised watercraft were increasingly designed for landing troops, material and vehicles, including by landing craft and for insertion of commandos, by fast patrol boats, zodiacs and from mini-submersibles. The term amphibious first emerged in the United Kingdom and the United States during the 1930s with introduction of vehicles such as Vickers-Carden-Loyd Light Amphibious Tank or the Landing Vehicle Tracked.

On 9 March 1847, during the Mexican–American War, the United States military made an amphibious landing and besieged the key Mexican seaport of Veracruz. The port surrendered twenty days later. The U.S. forces then marched inland to Mexico City.

March 9 is the 68th day of the year in the Gregorian calendar; 297 days remain until the end of the year.