|This article is about the technology in Age of Empires II. For other uses of the term, see 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. Spies is the only technology in the game to have a variable cost. The cost depends on how many Villagers, Trade Carts, Fishing Ships, and Transport Ships the enemy (including 'neutral' players) team has. 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.
Civilization bonuses Edit
"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."