The tercio was the product of the Italian Wars, in which the Spanish general, Gonzalo Fernández de Córdoba, reorganized the Spanish army throughout a series of conflicts at the end of the 15th century and early 16th century, into a tactically unique combination of combined arms centered around armored infantry.
Erhard Schön - Feldtwaybel (Veldwevel) - circa 1530 "Clas Feldtwaybel 'claims to have participated in the Battle of Pavia (1525). That was the decisive battle in the decades-long "Italian Wars," which many Swiss and German mercenaries fought. In Pavia Emperor Charles V won a resounding victory over the French King Francis I. According to this Clas was due to him. If veldwevel he was responsible for drawing up the battle.
Erhard Schön - Feldtwaybel (Veldwevel) - circa 1530