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This article is about the technology in Age of Empires II. For other uses of the term, see Spies.

Spies have infiltrated your nation.
—Message when an enemy player has researched Spies

Spies is a technology in Age of Empires II available at the Castle upon reaching the Imperial Age. Once researched, it allows the player to see the enemy's Line of Sight; if Cartography has not been researched, it also affects allies. Spies is (alongside Flemish Revolution) one of only two technologies in the game to have a variable cost.

The cost depends on how many civilian units (including ships and Flemish Militia transformed from Villagers via Flemish Revolution) that non-defeated non-allied (also includes allies if teams are not locked) players have. Each of those units increases the cost by 200 gold, with a minimum cost of 200 gold and a maximum cost of 30,000 gold. This technology is researched almost instantly.

Spies is considered to be one of the most useful technologies as it grants players a permanent view of enemy movements. However, Spies is substantially the most costly technology to research, more so in games with high population caps, which is why it is usually not affordable. However, in the late game when all but one team are almost finished off, Spies usually becomes affordable and helps speeding up the finish of the game. Presumably, this was the intention of the developers to include Spies in the first place, as without it, games on larger maps can end in long and pointless scouting missions.

It is disabled in Deathmatch mode games due to the massive amount of starting gold each player has, and in Regicide games, where it is replaced by Treason. Spies is not already researched in Post-Imperial matches.

Civilization bonuses[]


  • Originally, the technology did not include temporary allies. With some patch in the Definitive Edition, the cost of Spies includes allies too if teams are not locked. This was mostly done due to campaign scenarios in which, upon defeating a main enemy, the ally betrayed the player. Between the two events, Spies becomes very cheap. For example, in Bukhara, after the Huns were defeated and before the Gokturks betrayed the player, there was a small time window in which Spies cost the minimum.


Advanced civilizations of any age gathered information about potential enemies as part of their foreign policy. Much of this intelligence was gathered overtly through the normal channels of trade and diplomacy. Prudent civilizations with hostile neighbors actively enlisted spies and informants to monitor enemy activity. During the Middle Ages the Byzantines and Mongols were especially active in employing networks of agents among their enemies. Spies gave early warning of enemy forces marshalling for attack or searched for weaknesses in enemy defenses.
Technologies in Age of Empires II
Economic technologies
MaleVillDEFEMALEVILLDE VillagerWheelbarrowDE Wheelbarrow · HandcartDE Hand Cart
Aoe2de food FoodHorseCollarDE Horse Collar · HeavyPlowDE Heavy Plow · CropRotationDE Crop Rotation
GillnetsDE Gillnets
Aoe2de wood WoodDoubleBitAxe aoe2DE Double-Bit Axe · BowSawDE Bow Saw · TwoManSawDE Two-Man Saw
Aoe2de gold GoldGoldMiningDE Gold Mining · GoldShaftMiningDE Gold Shaft Mining
CaravanDE Caravan
Aoe2de stone StoneStoneMiningDE Stone Mining · StoneShaftMiningDE Stone Shaft Mining
Civilian shipsDryDockDE Dry Dock · ShipwrightDE Shipwright
Market aoe2DE MarketCoinageDE Coinage · BankingDE Banking
GuildsDE Guilds
Military technologies
GeneralConscriptionDE Conscription
HeresyDE Heresy · Devotion icon AoE2DE Devotion · FaithDE Faith
Melee unitsForging aoe2de Forging · IronCastingDE Iron Casting · BlastFurnaceDE Blast Furnace
CavalryBloodlinesDE Bloodlines · HusbandryDE Husbandry
ScaleBardingArmorDE Scale Barding Armor · ChainBardingDE Chain Barding Armor · PlateBardingArmorDE Plate Barding Armor
InfantrySuplliesicon Supplies · AoE2 Gambesons Gambesons · SquiresDE Squires · ArsonDE Arson
ScaleMailArmorDE Scale Mail Armor · ChainMailArmorDE Chain Mail Armor · PlateMailArmorDE Plate Mail Armor
Ranged unitsBallisticsDE Ballistics · ChemistryDE Chemistry
FletchingDE Fletching · BodkinArrowDE Bodkin Arrow · BracerDE Bracer
ArchersPaddedArcherArmorDE Padded Archer Armor · LeatherArcherArmorDE Leather Archer Armor · RingArcherArmorDE Ring Archer Armor
ThumbRingDE Thumb Ring · ParthianTacticsDE Parthian Tactics
SiegeSiegeEngineersDE Siege Engineers
ShipCareeningDE Careening · DryDockDE Dry Dock
ShipwrightDE Shipwright
WarGalleyDE War Galley
BuildingTownWatchDE Town Watch · TownPatrolDE Town Patrol
Masonry aoe2de Masonry · ArchitectureDE Architecture
HeatedShotDE Heated Shot · ArrowSlitsDE Arrowslits · MurderHolesDE Murder Holes · TreadmillCraneDE Treadmill Crane · HoardingsDE Hoardings · BombardTower aoe2DE Bombard Tower
HerbalDE Herbal Medicine
MonkRedemptionDE Redemption · AtonementDE Atonement · SanctityDE Sanctity · FervorDE Fervor · IlluminationDE Illumination · BlockPrintingDE Block Printing · TheocracyDE Theocracy
MaleVillDEFEMALEVILLDE VillagerLoomDE Loom · SapperDE Sappers
Miscellaneous technologies
SpiesDE Spies · SpiesDE Treason · UniqueTechCastle-DEUniqueTechImperialDE Unique technologies
Removed/cut generic technologies
Bombardcannonresearch Bombard Cannon · CannongalleonresearchDE Cannon Galleon · Cartography aoe2de Cartography · Handcannon Hand Cannon · Huntingdogs Hunting Dogs · Revetments · TrackingDE Tracking