military unit composed of pikesmen, cavalry, infantry, and artillery

The standard pike and shot formation of the late 16th and early 17th C. Everything from 3000 man squares with shot on the corners to 1000 man blocks with "sleeves" of shot. Replaced in the 1630s and 1640s with Dutch-style battalions.

Tercio (Also known as "Spanish Tercios") was a term used by the Spanish army to describe a mixed infantry formation of about 3,000 pikemen and musketeers, sometimes referred to by other nations as a Spanish Square. It was a formalisation of the organisation and fighting techniques that had been developed principally by Gonzalo Fernández de Córdoba, during the Italian Wars. It marked the transformation of medieval military institutions into the early modern combined-arms army with a focus on infantry.