On 27 July, Gotovina reinforced the Bosansko Grahovo axis by deploying the 4th Guards Brigade on the right flank. The brigade broke through the VRS defence in its sector, advancing about and arriving within of Bosansko Grahovo. Advances in the Glamoč area were still being achieved slowly. The Croatian Air Force took part in the attack the same day, using two MiG-21s to conduct airstrikes designed to disrupt the road network around Glamoč, violating a no-fly zone imposed by the UN and enforced by NATO as Operation Deny Flight.