That month, 21 boats fought a battle with two formations; Convoys ONS 18/ON 202. The battle was a failure. In October an attack on Convoy SC 143 failed, even with limited air support from the "Luftwaffe". The battle with Convoys ONS 20/ON 206 in the same month was a comprehensive defeat. A fourth major battle, Convoy SL 138/MKS 28, developed in the last days of October and ended in another failure for Dönitz. The November battle around Convoy SL 139/MKS 30 ended in the repulse of 29 U-boats with the loss of only a single ship. Intelligence proved its worth. During the battles of convoys ONS 18/ON 202, Dönitz's admonitions to his commanders allowed the Allied intelligence services to uncover German tactical intentions. Dönitz had tried and failed to push his forces through lethal convoy defences. The hunter-killer groups were called in to hunt the remaining members of the wolfpacks, with predictable results. In mid-December 1943, Dönitz finally conceded not only the Atlantic, but the Gibraltar routes as well.