The tercio (Spanish pronunciation: [ˈterθjo], Portuguese: terço [ˈteɾsu], "third") was a Renaissance era military formation made up of a mixed infantry formation of about 3,000 pikemen, swordsmen and arquebusiers or musketeers in a mutually supportive formation. It was also sometimes referred to as the Spanish Square or Tercio Español. It was widely adopted and dominated European battlefields in the sixteenth century and the first half of the seventeenth century.