The invasion of central Mexico
Once the American army was ashore below Veracruz it moved quickly to surround the city and its defenses, establishing siege lines by St. Patrick’s Day, 1847. The Mexican fortifications included Fort Santiago, located to the south of the city and Fort Concepcion to the north of the city, on an elevated position. Fort San Juan de Ulua was constructed on a reef offshore from the town, and was not directly attacked by the Americans, other than by long range bombardment from naval ships. As the Americans moved into position they repelled sorties from the Mexican garrisons, and placed troops further inshore to prevent Mexican reinforcements from reaching Veracruz.
On March 22 the American artillery began a systematic bombardment of the town and fortifications, supported by naval gunfire. The walls of the fortification were largely built of coral, mined from the reef outside the harbor, and the heavy naval guns made short work of them. US troops and ships fired rockets over the walls of the fortifications, which did relatively little damage, but were effective in creating a sense of terror among both civilians and the besieged troops. On March 24 a relieving force of 2,000 Mexican troops were encountered by American troops and driven back in sharp fighting. With no possibility of relief the Mexican commander, Juan Morales, requested a parley.
Morales asked for a cease-fire to allow the evacuation of civilian women and children from the city on March 25. American commander Winfield Scott refused and again demanded the city surrender. On the evening of March 25 Morales resigned his command rather than acceding to the recommendation of his officers that he surrender the post. He was replaced by General Jose Landero. On the morning of March 26 Landero requested terms from Scott. Veracruz and its fortifications, including San Juan de Ulua, were handed over to the Americans on March 28, and Scott established garrisons for the city before setting out on the road to Mexico City.
Scott began moving the American army inland on April 2, sure that the city and port were safe from attack. At the same time, Mexican General Santa Anna was moving east. Scott’s army consisted of about 8,500 men, while Santa Anna commanded just over 12,000. Santa Anna positioned his army in a fortified mountain pass near Xalapa, northwest of the city of Veracruz, which was known as Cerro Gordo. The leading elements of Scott’s army arrived on April 12, and engineers scouted the position for the best placement of American artillery. One of the engineers, Lieutenant Pierre Gustavus Beauregard, observed that the taking of neighboring Atalaya Hill would make the Mexican position untenable.
In order to take the hill roads were necessary to enable the placement of artillery. The Army Corps of Engineers officers, under the supervision of Captain Robert E. Lee, created a road up the steep slopes of the hill under the cover of darkness, and artillery was moved into possession by manpower alone, since the slopes were too sleep for mules and horses. One by one the guns were moved into position to cover an infantry assault on Atalaya Hill, which was taken on April 17. The assault allowed American troops to effectively surround the Mexican Army, attacking it from the rear. By ten in the morning of April 18, most of the remaining Mexican troops had either fled or surrendered.