Players can gather secret military information from other kingdoms through espionage prior to planned attacks. Espionage is achieved by sending spies to a kingdom's center or other owned places. Spies can supply information only for the place to which they are sent.

Spies at a place also reveal out enemy spies sent by another kingdom. Consequently, only spies can prevent a place from being spied. In these situations, the kingdom with the higher spying power succeeds. The result of the spying process is received in a spy report.

Spies are produced at the spy office found at the kingdom center. A kingdom can not produce spies at conquered places (colonies and cities), but can only import spies to there from the kingdom center.