Battle of the Bulge, there is a popular misconception that entire line just crumbled in the face of mighty Panzers with only 101st and fuel shortages preventing the Germans from driving all the way to the sea, before Patton and clear weather came to the rescue.
In reality American defending forces fought hard, but were pushed back by enemy superiority as it usually happens during offensives, with the most important action being the defense of Elsenborn ridge.
German strategy didn't rely on capture of American fuel depots, those were seen as welcome bonus, they relied on German final fuel reserves, but had trouble bringing this fuel forth, once the advance began, due to traffic jams, courtesy of poor roads in the region, American demolitions and dogged defense of Elsenborn ridge and Bastonge, not to mention the air interdiction once the skies cleared.
Kampfgruppe Wittman didn't conduct the deepest penetration of allied lines, that feat goes to the 2nd Panzer division of the mundane Wehrmacht, which advanced within the sight of Meuse before being pushed back by American counterattack (with British support).