Political map of North America & the Caribbean 9 March 1847 (Siege of Veracruz): Despite the US victories in the north (Mexican-American War), the Mexican army remained intact. Rather than continuing to march south, the US decided to bypass these forces by mounting an amphibious landing at Veracruz and marching west into the Mexican heartland (Mexico City Campaign). With Mexico unable to send reinforcements in time, Veracruz fell to a 20-day siege (Siege of Veracruz).