Tercio

The tercio ( "third") or tercio español ("Spanish third") was a Spanish military unit of the Spanish Empire during the era of the dominance of Habsburg Spain in Europe and the Renaissance era. The tercio was an infantry formation made up of pikemen, swordsmen and arquebusiers or musketeers in a mutually supportive formation, that in theory was up to 3,000 soldiers, although it was usually less than half this size. It was also sometimes referred to as the Spanish Square in other countries and the formation was also much used by other powers, especially the Imperial Army of the Holy Roman Empire.