The term 'Montezuma Subject' refers to the AZTEC people, an indigenous group of people who lived in what is now Mexico. They were one of the most powerful civilizations in Mesoamerica and their culture was highly influential in the region. The Aztecs were known for their advanced architecture, art, and religious practices. They also developed a complex system of government and had a strong military. The Aztecs were eventually conquered by the Spanish in the 16th century.