<P> Rather than reinforce Taylor's army for a continued advance, President Polk sent a second army under General Winfield Scott, which was transported to the port of Veracruz by sea, to begin an invasion of the Mexican heartland . On March 9, 1847, Scott performed the first major amphibious landing in U.S. history in preparation for the Siege of Veracruz . A group of 12,000 volunteer and regular soldiers successfully offloaded supplies, weapons, and horses near the walled city using specially designed landing crafts . Included in the invading force were Robert E. Lee, George Meade, Ulysses S. Grant, James Longstreet, and Thomas "Stonewall" Jackson . </P> <P> The city was defended by Mexican General Juan Morales with 3,400 men . Mortars and naval guns under Commodore Matthew C. Perry were used to reduce the city walls and harass defenders . After a bombardment on March 24, 1847, the walls of Veracruz had a thirty - foot gap . The city replied the best it could with its own artillery . The effect of the extended barrage destroyed the will of the Mexican side to fight against a numerically superior force, and they surrendered the city after 12 days under siege . U.S. troops suffered 80 casualties, while the Mexican side had around 180 killed and wounded, about half of whom were civilian . During the siege, the U.S. side began to fall victim to yellow fever . </P> <P> Scott then marched westward on April 2, 1847, toward Mexico City with 8,500 healthy troops, while Santa Anna set up a defensive position in a canyon around the main road about 50 miles (80 km) north - west of Veracruz, near the hamlet of Cerro Gordo . Santa Anna had entrenched with 12,000 troops, and artillery that were trained on the road, where he expected Scott to appear . However, Scott had sent 2,600 mounted dragoons ahead and they reached the pass on April 12 . The Mexican artillery prematurely fired on them and therefore revealed their positions, beginning the Battle of Cerro Gordo . </P> <P> Instead of taking the main road, Scott's troops trekked through the rough terrain to the north, setting up his artillery on the high ground and quietly flanking the Mexicans . Although by then aware of the positions of U.S. troops, Santa Anna and his troops were unprepared for the onslaught that followed . In the battle fought on April 18, the Mexican army was routed . The U.S. Army suffered 400 casualties, while the Mexicans suffered over 1,000 casualties and 3,000 were taken prisoner . In August 1847, Captain Kirby Smith, of Scott's 3rd Infantry, reflected on the resistance of the Mexican army: </P>

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