Ninja

The Ninja is a Mercenary unit that can be trained from the Saloon/Monastery or sent from the Home City in Age of Empires III: The WarChiefs and The Asian Dynasties.

Overview
Ninjas are infantry units that are very effective against Heroes (explorers, for example) and mercenaries. Ninjas themselves are mercenaries, so are easily countered by spies or other ninjas.

The Ninja can also use Stealth Mode, which is detected by an Explorer or Town Center (or other units). There is a more powerful ninja, the Consulate Ninja, which costs export and is unique to the Japanese.

Compared to the Spy
The Ninja differs from the Spy in that it is classified as a mercenary, in contrast to a Spy, making the Spy very effective against Ninjas. The Ninja also has slightly less speed, higher cost, much lower Line of Sight and much lower multipliers, except against Native Warriors, but it has more hit points and much more (siege) attack. Overall, Ninjas are more well-rounded than Spies, and more deadly against Native Warriors, but less lethal against mercenaries and heroes, and less proficient in scouting.

Accessibility
The Ninja also has different accessibility compared to Spies, as Spies are always available from the Church/Mosque from the Colonial Age onward (except for the Dutch Church from the Japanese Consulate), can be sent from the Home City by European civilizations, or 4 can be sent from the British once at the expense of export using the consulate, while the Ninja can sometimes be trained at the Saloon/Monastery, or sent with Home City shipments by certain civilizations.