You can train these units after you have annexed the Empire where they are uniquely developed for.
Spanish Guerrillas
The elite Infantry unit of the Spanish army, with excellent ranged attacks and melée combat.
The Spanish Guerrillas are a unit formed by civilians
who do not belong to the regular army but who, by making
use of their knowledge of the land, employ tactics such
as ambushes and skirmishes. These skills allow them to
confront armies which are militarily superior.
Portuguese Caçadores
Elite Portuguese Infantry unit capable of both ranged attacks and melée combat.
Portuguese Caçadores are considered the finest harassment
and skirmishing unit of the era. Any general would welcome
these highly skilled men into his ranks.
Mamelukes
Elite Egyptian Cavalry unit, fierce in melée combat, but incapable of ranged attacks.
The Mamelukes are the elite Cavalry of the
Egyptian army. Fierce and much feared by the
enemies of Islam, they are famed for their
devastating charges and deadly scimitars.
Polish Lancers
Elite Polish Cavalry unit, possessed of the finest defence and melée combat of any class of Cavalry, but incapable of ranged attacks.
Considered the finest Lancers of the era, Polish
Lancers are the unit most skilled at charging other
Cavalry or even Infantry squares.