From Halopedia, the Halo wiki
2000 thousand Mexican soldiers attacked 155 Texan men at the Alamo. 600 Mexican soldiers were killed along with a number of Texans. Though there were survivors. The battle was referenced in regards to the one sided nature of the early Human-Covenant War in Historical/Psychological Analysis of Cole, Preston J.
When the Covenant attacked Earth in late 2552, Mexico became a site of conflict during the global battle. That is to say that the Covenant deployed troops just off the coast of the Yucatán Peninsula. These Covenant forces intended to search the seafloor there for unknown reasons, but their operation was stopped by the Spartan-IIs of Blue Team.
List of appearances