How did halls of Montezuma get into the marines battle hymn?

Answer 1

Army General Winfield Scott marched on Mexico City in 1847 with a force of about 12,000 to 13,000 men. His army included one battalion of Marines, which battalion numbered less than 400 officers and men. The Army fought three battles before Mexico City, Contreras, Churusbusco and El Molino del Rey. While soldiers fought those battles, the Marine battalion guarded the army's supply wagons.

The Marine battalion was part of one assault column in the assault on Chapultepec. According to USMC records, the Marine battalion was halted short of the walls of Chapultepec. From that point, the Marine battalion held its position and supported the attack by firing on the walls of Chapultepec. The troops who scaled the walls and captured the castle were Soldiers, not Marines. No Marine ever got into Chapultepec during the actual assault.

After the fall of Chapultepec, General Worth and General Quitman(whose division included the Marines) ordered their respective Divisions to advance down two causeways and capture two of the gates of the city. The Marines joined those advances. After the fall of Chapultepec, the Mexican army abandoned Mexico City to the Americans. American troops, including the Marines, took control of the city.

So, the line about the Halls of Montezuma signifies nothing more than that a battalion of Marines was present when Soldiers defeated the Mexican Army and captured Mexico City, nothing more.