The term "Tercio" refers to a military unit that was prominent in Spain during the 16th and 17th centuries. These units were known for their effectiveness in battle, combining infantry, cavalry, and artillery. The Tercio played a crucial role in the Spanish Empire's military campaigns, particularly during the Thirty Years' War. Tercio units were characterized by their unique formation and tactics, which allowed them to adapt to various combat situations. They typically consisted of pikemen and musketeers, working together to create a formidable fighting force. The success of the Tercio influenced military organization in Europe for many years.