Espionage is a gameplay mechanics included in the Civilization V: Gods and Kings expansion pack. This mechanics introduces a new level of covert actions in the game, which will have effects on technological advancement, diplomacy and even City-State relations.
Spy recruitment and mechanics
Espionage starts in a game once any civilization enters the Renaissance Era - every civilization then recruits their first Spy at the same time. After that, whenever any civilization enters a new Era, they get an additional Spy. Also, building the National Intelligence Agency provides an extra Spy for whoever built it.
Spies can be moved into cities from their secret Hideout. You can only target cities you've discovered on the map. The movement takes only 1 turn. After that, they take 3 turns to establish a surveillance network, after which they start their activities in the selected city and continue until given different orders.
Spies may die during their activities (Killed in Action). This happens when they try to steal a Technology and encounter an enemy Spy doing counter-intelligence, or when they organize an unsuccessful coup in a City-State. Killed spies are replaced after some turns by new recruits.
You may boost your Espionage and counter-espionage by building certain buildings or wonders - The Constabulary and the Police Station diminish the success rate of enemy spies attempting to steal technology in the city where they're built by 25% each; the Great Firewall Wonder makes technology theft in your whole empire close to impossible; and the National Intelligence Agency National Wonder levels up all your existing spies and decreases the effectiveness of enemy spies, besides giving you an additional Spy.
In Brave New World any Spy may be re-qualified as a Diplomat when moving him into the capital of another civilization. A Diplomat has different uses than a Spy, mainly related to the new World Congress mechanics. Note that a Diplomat can go back to being a Spy by moving him again (the dialogue opens each time you move the Spy). Check the World congress article for more info.
Spy abilities and activities
What the spy actually does depends on where he's assigned to. There are four possible spy activities:
- Technology theft - If you assign a spy to another civilization's city, he starts spying on that civilization, and at the same time tries to steal their technology. While in that city, your spy will also give you vision of it and the two tiles surrounding it.
Before assigning them, your spies will evaulate the science potential of each city, which depends on the number of citizens, and the presence of any anti-spy building (Constabulary or Police Station). The greater the science potential, the faster the spy can steal a technology.
Depending on the technological level of the target civilization, on the science potential of the target city, and on the experience level of the spy himself, he will steal a technology within a number of turns. This technology is one that the target civilization already has, and you have yet to discover.
Be careful, though. In the turn when stealing the technology, the spy exposes himself to a certain degree. If he's inexperienced, and the enemy has good counter-intelligence measures in the city, they may discover the theft and who's responsible for it, leading to diplomatic outrage. Also, if there is an enemy spy in the city, he may discover and kill your spy, preventing the theft.
- Surveillance - While in another civilization's city, your spy automatically screens for their leader's intentions and activities. He will then warn you about their plans (For example: "X is secretly plotting against Y"), although depending on his experience level, he might not find many details about those plans. You may then use the information to gain some advantage, for example by warning the target about the plot.
- City-State manipulation - Stationing a spy in a City-State will set him to rig the local elections which occur regularly every 12 turns. If he's successful, the new City-State government will be more friendly to your civilization, and less friendly to others, meaning you'll gain Influence with the City-State, while others will lose it. Enemy spies may also be acting in the same City-State, and then the spy with better experience will have better chance to rig elections.
While in a City-State, your spy may also stage a coup. This is only possible when the City-State already has an ally. It is a dangerous course of action, because you risk losing your spy if the coup is unsuccessful. However, if successful, the City-State immediately allies itself with you, while their previous ally's Influence is reduced to the level of Influence you previously had on the City-State. The success rate of the coup tends to depend on your spy's experience level, the presence of other spies in the City-State, and your current influence level with them (the higher your influence, the more chance of a success).
- Counter-intelligence - Stationing a spy in one of your own cities will have him doing counter-intelligence work. Whenever there is an enemy spy acting there, your spy will have a chance to discover and kill him.
Leveling up your spies
Every spy can gather experience while acting, and reach higher levels. He starts at level 1 - Recruit. He then moves to level 2 - Agent, and finally, to level 3 - Special Agent. For each higher experience level, the spy becomes more effective - He takes less turns to steal technologies, has higher success rate of election rigging and coups, and better chance to discover enemy spies (and kill them).
Leveling up happens each time the spy successfully steals a technology (whether or not he's partially discovered), and each time he kills an enemy spy. Apparently, rigging elections and staging coups aren't that important.
Espionage may become very helpful to your civilization, if used wisely. If your science output is lagging, station one of your Spies in the capital of the fastest technology-researching civilization, and start making up for your low science output by stealing techs! If, on the other hand, your research is going pretty strong, and few other civilizations can match you, station your Spies in key City-States to gain influence with them, but don't forget to spare a spy (or two) to be stationed in your Capital (or one of your other cities with high potential) to make sure no one steals your technologies.
The English civilization is especially effective at spying, because they get an extra spy as soon as any civilization enters the Renaissance Era. When playing as England, you should make sure you are using this advantage and expand it.
Brave New World
Civilization V: Brave New World expands on the Espionage mechanics introduced in Gods and Kings, and introduces a new type of Spy called Diplomat, which is placed in another civilization's Capital and allows for more advanced diplomatic trading options, specifically in regard to the new World Congress feature.