Defensive structure

A Bombard Tower and standard Tower behind a Wall in Age of Empires II: Definitive Edition.

Defensive structure is a type of building available in every game of the Age of Empires series. Rather than be used to train units or research technologies, they are used to defend their civilization from attacks, or warn it of attacks.

Generally speaking, there are three types of defensive structures: Walls, towers, and Castle-type buildings.

List of defensive structures

Age of Empires

All defensive structures are researched and upgraded from Granary:

• Watch Tower
• Sentry Tower
• Guard Tower
• Ballista Tower
• Small Wall
• Medium Wall
• Fortification

Towers found in the campaign and the Scenario Editor:

• Zenobia's Tower
• Mirror Tower

Age of Empires II

Constructable

•  Outpost
•  Watch Tower
•  Guard Tower
•  Keep
•  Bombard Tower
•  Palisade Wall
•  Palisade Gate
•  Stone Wall
•  Fortified Wall
•  Gate
•  Castle
•  Krepost (Bulgarians only)
•  Donjon (Sicilians only)

Unconstructable

The unconstructable defensive structures can only be found in the Scenario Editor.

• Fence
• Fortified Palisade Wall
• Barricade
• City Wall
• Sea Wall
• Sea Gate
• Sea Tower
• Fire Tower
• Fortified Tower
• The Accursed Tower
• The Tower of Flies
• Fortified Tower
• Poenari Castle
• Fortress

Age of Mythology

All defensive structures (except for fully upgraded walls) can research technologies that upgrade themselves. Towers can also research technologies that improve building Line of Sight.

• Sentry Tower
• Watch Tower (Egyptians only free automatically upgrade Classical Age)
• Guard Tower (except Norse Heroic Age)
• Ballista Tower (Egyptians only Mythic Age)
• Wooden Wall
• Earthen Wall (Chinese only Archaic Age)
• Stone Wall (Classical Age)
• Fortified Wall (except Norse Heroic Age)
• Citadel Wall (Egyptians only Mythic Age)
• Great Wall (Chinese only Mythic Age)
• Bronze Wall (Atlantean Classical Age)
• Iron Wall (Atlantean Heroic Age)
• Orichalkos Wall (Atlantean Mythic Age)
• Mirror Tower (Atlantean only available through the worship of Helios, except Gaia)

Age of Empires III

• Town Center (only against ships except when garrisoned by villagers)
• Dock (only against Ships when garrisoned by Fishing Boats)
• Outpost (European civilizations only, except Russians)
• Blockhouse (Russians only, Chinese and Indian campaign with Russian Consulate ally)
• War Hut (Native American civilizations only)
• Castle (Asian civilizations only)
• Trading Post (With "Advanced Trading Post" Home City Card)
• Tambo (Incas only)
• Wall (all civlizations except Sioux)
• Gate (all civlizations except Sioux)
• Nobles' Hut (Aztecs only)
• Kallanka (Incas only)
• Fort (European civilizations only, with Home City Card, Chinese and Indian campaign with Russian Consulate ally)
• Agra Fort (Indian Wonder)
• Stronghold (Incas only)
• Fixed Gun (Campaign and Scenario Editor only)
• Asian Outpost (Campaign and Scenario Editor only)

Civilization bonuses

Age of Empires

• Babylonians: Walls and towers +60% hit points.
• Choson: All towers have +2 range
• Romans: -40% tower building cost
• Shang: All walls have +60% hit points.

Age of Empires II

• Aztecs: Castles train military units 11% faster.
• Bulgarians: Can build the Krepost.
• Byzantines: Defensive structures have +10%/+20%/+30%/+40% HP in the Dark/Feudal/Castle/Imperial Age.
• Franks: Castles are 25% cheaper.
• Incas: Defensive structures cost -15% stone.
• Koreans: Tower upgrades are free (Bombard Towers require Chemistry).
• Sicilians: Castles are constructed 100% faster, can build the Donjon.
• Teutons: Towers garrison twice as many units, Murder Holes is free.
• Turks: The Bombard Tower technology is 50% cheaper

Age of Empires III

• Russians: Can build Blockhouses, which combine the functions of the Outpost and the Barracks.