Defensive structure

A Bombard Tower and a Keep 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.

In Age of Empires II, Age of Empires III, and Age of Mythology, Town Centers get an attack of their own that can be improved by garrisoning Villagers or Archers and double as defensive structures as a result, even though their primary function is economic.

Age of Empires

All defensive structures are researched and upgraded from the Granary:

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

Towers found in campaigns and in the Scenario Editor:

• Zenobia's Tower
• Mirror Tower

Civilization bonuses

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

Age of Empires II

Constructable

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

Unconstructable

The unconstructable defensive structures can only be found in campaigns and 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
• Poenari Castle
• Fortress

Civilization bonuses

• Aztecs: Castles train military units 11% faster.
• Bohemians: Chemistry is available in the Castle Age.
• Britons: Town Centers cost -50% wood (starting in the Castle Age).
• Bulgarians: Town Centers cost -50% stone and can build Kreposts.
• Byzantines:
  • Defensive structures have +10%/+20%/+30%/+40% HP in the Dark/Feudal/Castle/Imperial Age.
  • Town Watch and Town Patrol are free.
• Chinese:
  • Town Centers support ten population (instead of five) and have +5 Line of Sight.
  • Defensive technologies are 10%/15%/20% cheaper in the Feudal/Castle/Imperial Age.
• Cumans: Can build a second Town Center in the Feudal Age.
• Franks: Castles are 25% cheaper.
• Incas: Defensive structures cost -15% stone.
• Koreans: Tower upgrades are free (Bombard Towers require Chemistry).
• Malay: Can upgrade their Docks to defensive structures (Harbors).
• Malians: Defensive structures cost -15% wood.
• Persians: Town Centers have double HP and work 10%/15%/20% faster in the Feudal/Castle/Imperial Age.
• Portuguese: Defensive technologies are researched 30% faster.
• Sicilians: Castles and Town Centers are constructed 100% faster, can build Donjons.
• Spanish: Defensive structures are built 30% faster.
• Teutons:
  • Towers can garrison twice as many units, Town Centers can garrison +10 units.
  • Murder Holes and Herbal Medicine are free.
• Turks: Chemistry is free and the Bombard Tower technology is 50% cheaper.
• Vietnamese: Conscription is free.

Team bonuses

• Cumans: Palisade Walls have +33% hit points.
• Ethiopians: Towers and Outposts have +3 Line of Sight.
• Mayans: Walls are 50% cheaper.
• Teutons: Towers are more resistant to conversion.

Unique technologies

• Artillery: +2 range for Bombard Towers (Turks)
• Crenellations: +3 Castle range; Garrisoned infantry fire arrows (Teutons)
• Cuman Mercenaries: Each team member can train 10 free Elite Kipchaks from their Castles (Cumans)
• Great Wall: +30% Wall and Tower HP (Chinese)
• Kasbah: +25% Castle work speed for team (Berbers)
• Panokseon: +2 Watch Tower line range (Koreans)
• Stronghold: +25% Tower and Castle attack rate (Celts)
• Timurid Siegecraft: Flaming Camels can be trained from Castles. (Tatars)
• Yasama: Towers fire 2 additional arrows (Japanese)
• Yeomen: +2 Tower Attack (Britons)

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.

• Town Center
• 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
• Dock (only against ships when garrisoned by Fishing Boats)
• Outpost (European civilizations only, except Russians)
• Blockhouse (Russians only, Indian campaign and Chinese 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 civilizations except Lakota)
• Gate (all civilizations except Lakota)
• Nobles' Hut (Aztecs only)
• Kallanka (Incas only)
• Fort (European civilizations only, with Home City Card, Indian campaign and Chinese 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)