ak interactive historica spanish tercios soldier resinScale 65mm. The origin of the Spanish Tercios as such dates back to the reign of Charles I in 1534 and represents the culmination of a military renewal initiated some time before by the Catholic Monarchs under the command of the Great Captain. The Spanish Tercios were from their birth and for almost two centuries, the most lethal infantry in Europe. Their fearsome efficiency derived from an exceptional combination of firearms (arquebus and musket)