During which conflict did Marines occupy the "Halls of Montezuma"?

The occupation of the "Halls of Montezuma" refers to the events during the Mexican War, specifically the Battle of Chapultepec in 1847. During this battle, U.S. Marines, alongside American forces, played a crucial role in capturing Chapultepec Castle in Mexico City, which was often symbolically referred to as the "Halls of Montezuma." This conflict was significant in American military history and became a point of pride for the Marine Corps. The term has since been immortalized in the Marines' hymn, highlighting the enduring legacy of their involvement in this pivotal moment of the Mexican War. This context underscores why the choice regarding the Mexican War is the correct answer to the question.