Guerrilla war and the threat of American veterans

Failure to broaden domestic support would leave Maximilian vulnerable to being seen as a foreign ruler. Guerrilla warfare would then absorb French troops needed to secure the external frontier. Experienced American volunteers could enter Mexico while those troops were occupied elsewhere, as veterans had done historically. Their years of combat experience could strengthen the opposition. This division between internal fighting and border security makes a larger Mexican army important to the proposed settlement.