with the regular air force tanker fleet being used more and more in southeast asia after 1965 to support combat operations in south vietnam, combined with the concurrent demands of the strategic air command (sac) for performing its nuclear deterrence mission, both volunteer air force reservists and air national guardsmen in air refueling units participated in worldwide air refueling missions during their annual training or other additional active duty periods in order to supplement the active duty tanker force. the texas air national guard's 136th air refueling wing inaugurated operation creek party on 1 may 1967, because the regular air force did not have enough kc-135 stratotanker aircraft available in europe to train its fighter pilots in usafe. the operation eventually involved nine ang air refueling groups that rotated approximately every two weeks to rhein-main air base in west germany.