Espionage, the practice of gathering information through covert means, was a common tactic used by the Roman military. The Roman legions and armies of occupation would often use informers and spies, but not in a formal or organized manner. This was particularly true in the city of Rome, which was known for its whispers and endless conspiracies. One notable group of spies in ancient Rome was the frumentarii, who were possibly established by Emperor Domitian.