a1 Trinity College, Cambridge
Among the accusations Procopius brings against Justinian in the Secret History is the following:
The matter of the kataskopoi is as follows. From ancient times many men were maintained at public expense. They would enter enemy territory and gain access to the palace of the Persians, either under the guise of trading or by some other ploy. After investigating everything thoroughly, they would return to Roman territory and be able to report all the secrets of the enemy to the government officials. Forewarned, they were on their guard and nothing unforeseen would take them by surprise.