The Crimean Tatars who acted as Ottoman reinforcements on the Hungarian front during the 16th and 17th centuries had the task of making attacks and incursions on their enemy’s borders. The Turkish and Tatar sources hardly make any reference to the tools they had at their disposal and to how they collected information about the lands they had to attack and the armies they were likely to encounter. From the little evidence that we have one can only presume that the Tatars got their information directly from the theatre of war by forcing people of the conquered territories to spy and make guidance for the Tatar army. The knowledge that we present here has been gained from a report of 15 September 1663 made on the basis of the testimony of a captured spy working for the Tatars. From his testimony it becomes evident that the Tatars had an extensive spying network which had been organised by a German soldier in their pay, and that the Tatars paid the spies for their service and also rewarded them with a portion of their spoils. The captured spy’s testimony refers not only to the 1663 Ottoman campaign but also provides answer for an old historiographical problem. The Turkish traveller Evliya Çelebi reported on what he knew about the Tatars’ incursions and while doing so he attempted to give information on similar activities in far away territories like Brandenburg, Holland and even Sweden. Researchers agree that Evliya Çelebi never actually visited these countries, but one can suppose that he gleaned information from discussions with spies who worked for the Ottomans and Tatars.