MEXICO CITY
September 13th, 1847
"I knew I could not be wrong, so long as the enemy in large
numbers were ahead" Captain George H. Terret "I believe if we were to plant our batteries in hell the
Yankees would take them from us" Santa Anna, after the fall of Chapultepec "God is a Yankee" was his Chief of Staff's reply The assault on Mexico City was the culmination of a three year war between the USA and Mexico. The proximate cause of the war was the election of James K. Polk to the presidency in 1844, on an expansionist platform. At this time Texas, New Mexico, Arizona and California belonged to Mexico, but the resident American whites were keen to join the United States of America.
The war started in April 1846, and the US Navy quickly blockaded all major ports on both coasts of Mexico, which had no navy to speak of. At this time the marines were an integral part of the navy, and their main task was to guard ships and ports. They numbered about 1,000 men. The Navy, aided by the Americans already in California, eventually conquered San Francisco, Los Angeles and San Diego, securing the future state. The next step was to invade Mexico and force it to peace. Major General Winfield Scott commanded the American Army in this incursion. He was persuaded by Henderson to include Marines in the invasion force, since they were a permanent trained force, and many of Scott's volunteers had served their time and returned home.
When the Army reached Mexico City on the August 8th, 1847, the Marines were disgusted at having been used to guard the supply trains, thus missing the battles (such as they were) so far. The battalion of 357 men was commanded by Lieutenant Colonel Samuel E. Watson, and was attached to the division of Brigadier General John A. Quitman.
Scott's Army numbered 10,738 men, and faced a Mexican army of about 32,000 commanded by the self-styled Napoleon of the Americas, Santa Anna. The Mexicans were massed south of the city (the direction from which the Americans were approaching), so Scott decided to attack from the west. On 7th of September he used Brigadier General William J. Worth's division to assault a group of heavy stone buildings called Molino del Ray, which guarded the western approaches and were resolutely defended by the Mexicans. They took it, but ruined the division in doing so.
On Monday, September 13th the attack proper started. The first and main obstacle was Chapultepec, a steep hill surrounded by walls. It was defended by about 900 soldiers and a handful of cadets - known ever afterwards to Mexicans as the Ni§os Heroicos. Quitman's division was assigned the difficult south face, as a diversion from the main attack by Brigadier General Gideon Pillow's division up the west face. To the east of the hill, the Mexicans had garrisoned a vital road junction with a battery of artillery and some entrenched infantry.

The attack was a success. Special storming parties, including some Marines, were formed and equipped with ladders and pick-axes. These were to take the lower walls while the bulk of each division provided covering fire. They were quickly pinned down under the intense crossfire from the walls and from the force at the road junction. Then, by sheer persistence the pioneers of Pillow's division won the walls, and the brigade on the right flank cleared the road junction. The bulk of both divisions, including some Marines, swept up the hill and captured the fortress. Captain George H. Terret took his company of about 30 Marines and raced up the western causeway towards the San Cosme gate, the last defended position before Mexico City proper. Joined by one Ulysses S. Grant and about 20 men, they stopped a counter-attack by some Mexican lancers, then routed a force of over 1,000 enemy foot en route. Heavily outnumbered, they assaulted and took the gate against determined resistance, becoming the first troops to set foot in Mexico City itself. They had far outrun the rest of the Army, and were forced to return to the road junction. This gate was eventually re-taken by Worth's division that evening.
The rest of the Marines, with Quitman's division, advanced along the eastern causeway and established themselves inside the Belän gate before nightfall, after a fierce fight. The Mexicans counter-attacked several times, but could not press home against the American artillery and musketry. Overnight the city fathers persuaded Santa Anna to abandon the city to prevent damage to the buildings and civilian population. By morning the Americans discovered that the Mexicans had withdrawn and abandoned the city out of consideration for the populace, and the low morale of the Mexican army and its commanders.
Up until this time the Marine standard had borne the motto:
"To the Shores of Tripoli". On their return to Washington the people of that city presented the Marines with a new banner and a new motto: "From Tripoli to the Halls of the Montezumas". Thus a piece of Marine Corps history was born.