Tercio

The tercio 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.

Cross of Burgundy was adopted as the symbol of the Tercios and the Spanish Empire

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.

Spanish tercios were the first modern European army, understood as an army of professional volunteers, as opposed to the conscripted levies and hired mercenaries typical in other European countries of the time. The care that was taken to maintain a high number of "old soldiers" (veterans) in the units, and their professional training, together with the particular personality imprinted on them by the proud hidalgos of the lower nobility that nurtured them, made the tercios for a century and a half the best infantry in Europe. Moreover, the tercios were the first to efficiently mix pikes and firearms. The formation dominated European battlefields in the sixteenth century and the first half of the seventeenth century and is seen by historians as a major development of Early Modern combined armswarfare.