The whole battle of the bulge is a good metaphor for the saying. The germans pushed far past US lines. VERY far, yet they did not give up fighting, and they managed to eventually have a damn good defense that stopped the germansThe 101st was still able to mount effective resistance from their position though. To use an analogy, it's the difference between being outnumbered and besieged inside a castle whose walls are still intact and being in one whose walls have all collapsed and is now being overrun. In one the situation while dire is defendable and effective resistance is possible, in the other the fight is effectively over.