Tercio

A tercio (Spanish pronunciation: [ˈterθjo] "third") or tercio español ("Spanish third") was a Spanish infantry organization during the time that Habsburg Spain dominated Europe in the Early Modern era.

The tercio was an administrative unit with command of up to 3000 soldiers, subdivided originally into ten, later twelve compañías, made up of pikemen, swordsmen and arquebusiers or musketeers. These companies were deployed in battle and were further subdivided into units of thirty soldiers. These smaller units could be deployed individually or brought together to form what were sometimes called Spanish squares. These powerful infantry squares were also much used by other European powers, especially the Imperial Army of the Holy Roman Empire.

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. Tercio companies dominated European battlefields in the sixteenth century and the first half of the seventeenth century and are seen by historians as a major development of Early Modern combined arms warfare.

The use of massed pikes by Spanish armies began in the War of Granada (1482–92). During the Italian Wars, under the direction of the Spanish general Gonzalo Fernández de Córdoba, called "the great captain", the system of combined groups of pikeman, arquebusiers and swordsmen developed. The conflicts at the end of the 15th century and early 16th century evolved into a tactically unique combination of combined arms centered around armored infantry. To counter the French heavy cavalry, a colonelcy could theoretically have up to 6,000 men, but by 1534 this had been reduced to the tercio with a maximum of 3,000.

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