 Complete the following phrase:  The operation was launched on 16 December 1944 and enjoyed initial success, but it quickly suffered from a lack of air cover and the inexperience in some of its infantry component, and critically short fuel supply. Sixth SS Panzer Army met heavy allied resistance, and while Fifth Panzer Army managed to make a deep thrust into Allied line, Model was unable to exploit the breakthrough there. He had failed to capture a vital road junction at 