In contrast to the previous installments of Age of Empires series, the unit upgrades of every civilization in Age of Empires III usually do not change the original name of the unit, and in most of the cases only add a title word. A new upgrade becomes available in every Age. All unit upgrades take 30 seconds to complete.
The original installment is the only in which some unit's names were changed for the second upgrade.
The upgrade effect is always applied to the base units stats. Some of the units available in later ages have better base stats because they don't get the early upgrades, thus their later upgrades are more powerful in comparison.
Fortress Age Edit
The Fortress Age upgrade, titled Veteran for European civilizations, Elite for Native American civilizations, and Disciplined for Asian civilizations, adds 20% (25% for Native American civilizations) hit points and attack to the units.
Veteran/Elite/Disciplined upgrades cost 200 wood and 200 coin for European civilizations or 200 wood and 100 coin for Native American and Asian civilizations. For the Aztecs, Inca, and Iroquois who have two native warriors, the upgrade costs 300 wood and 200 coin instead.
Industrial Age Edit
The Industrial Age upgrade, titled Guard for European civilizations, Champion for Native American civilizations, and Honored for Asian civilizations, adds 30% (25% for Native American civilizations) hit points and attack to the units, for a total of +50% hit points and attack.
Guard/Champion/Honored upgrades cost 600 wood and 600 coin for European civilizations, Indian and Japanese; 300 wood and 300 coin for the Chinese; and 400 wood and 200 coin for Native American civilizations. For the Aztecs, Inca and Iroquois natives who have two native warriors, the upgrade costs 500 wood and 400 coin instead.
Royal Guard Edit
Some European civilizations' Industrial Age unit upgrades carry the title Royal Guard, which adds 40% hit points and attack to the units instead of 30%, for a total of +60% hit points and attack. This makes a civilization's Royal Guard units stronger than other civilizations' Guard units.
Hussar (King's Life Guard)
|Skirmisher (Needle Gunner)|
|Cavalry Archer (Tartar)|
Imperial Age Edit
The Imperial Age upgrade, titled Imperial for European civilizations, Legendary for Native American civilizations, and Exalted for Asian civilizations, adds 50% hit points and attack to the units, for a total of +100% hit points and attack (+110% in case of Royal Guard units and +75% in case of artillery).
Imperial/Legendary/Exalted upgrades cost 1,500 wood and 1,500 coin for European civilizations, Indians and Japanese; and 750 wood and 750 coin for the Chinese. For Asian civilizations, Exalted artillery upgrades cost 1,000 wood and 1,000 coin.
Auto upgrades Edit
Some units in Age of Empires III, usually those not trained in the normal way, upgrade automatically when reaching a new Age, instead of the upgrade having to be bought and researched.
The following units have this trait:
- Explorer Dog
- War Dog
- War Chief
- Skull Knight
- Dog Soldier
- Flying Crow
- Shogun Tokugawa