The Tercio ("one third"), also known as Tercio Español, was a Renaissance era military formation similar to and derivative of the Swiss pike square and was a term used to describe a mixed infantry formation of about 3,000 pikemen, swordsmen and arquebusiers in a mutually supportive formation; it was also sometimes referred to by other nations as a Spanish Square after its introduction by the Spanish army, and was widely adopted across international lines and dominated formalized field warf… (More on Tercio)