A war in Mexico would typically fall under the command of the Mexican government and its military forces, particularly the Secretary of National Defense (Secretario de la Defensa Nacional) and the Navy Secretary (Secretario de Marina). If the conflict involved international forces, such as U.S. troops, it would likely fall under the command of the U.S. military leadership, coordinated with the Mexican government, depending on the specifics of the situation and any agreements in place.
In any potential military engagements, multilateral organizations or alliances, such as NATO or the Organization of American States (OAS), could also play a role in facilitating coordination or issuing mandates depending on the nature of the conflict.