From 1975, as part of the operation code-named “Zapora” carried out by the Security Service, counterintelligence operations are documented as having been carried out with the aim of protecting facilities and units of the Polish and Soviet Army in Piła Voivodeship. Department II of KWMO/WUSW in Piła, in cooperation with WSW and MO, kept diplomats and foreigners from Western countries under surveillance. This control extended to the monitoring of all persons, regardless of nationality, in the areas adjacent to the facilities and those employed in enterprises providing services to the Polish Army. These persons of interest were identified as part of operational checks and registration questionnaires, using numerous secret collaborators and personal contacts. As a part of “Zapora”, major military exercises such as “OPAL 87” and “Przyjaźń 87” were also safeguarded. Operation „Zapora” was completed in January 1990.