192 The Great War overwhelming force against the left, that is in the face of the British during the early battles, were able to drive the Allies beyond the Somme before they could be reenforced. Had the Allies then re- mained behind the Laon-La Fere-Rheims barrier they would have been cut off from Paris and en- veloped. To avoid this they dismantled the forts and retired. It was of vital importance to the Allies, then, if they were to drive the Germans out of France after defeating them at the Marne to prevent them from halting before they passed this line of the Cham- pagne Hills, the sole naturally strong defensive posi- tion between the Marne and the Belgian frontier. Had they been able to do this they would have re- gained all that had been lost by their previous re- treat. But they did not quite succeed. In retaking Rheims they did drive the Germans from the east- ern end of the Champagne highlands, but the Ger- mans retained the hills just beyond Rheims, on which had stood the detached forts dismantled by the Al- lies in their retreat. It was from these hills that the Germans later bombarded Rheims cathedral. To the north the Allies did drive their opponents beyond the Aisne, and after desperate fighting won a foothold on the Craonne plateau south of the Lette. But the Germans were able to hang on at La Fere and Laon, that is, to the northern and highest edge of the Champagne Hills, where the French forts had stood.