SWIDWIN, Poland -- Pararescuemen with the 321st Special Tactics Squadron based out of Royal Air Force Mildenhall, United Kingdom recertify their fast roping insertion extraction system and repelling during a training exercise at Jackal Stone 10 Exercise 14 Sept. The 321st STS provide a fast reaction, rapidly-deployable force capable of establishing and providing positive control of the air to ground interface during special operations or conventional missions.