The End of the Great Retreat ij^ nificent courage and the remarkable efficiency of their soldiers and General Staff. But on the other hand Germany had reached the point where France must fight, the point from which French retreat might im- peril the existence of French military strength, as it would certainly cut her battle line in half. Under these circumstances and chiefly between Montmirail and Vitry-le-Francois the mass of the French and German armies about September 6 be- gan the desperate and tremendous Battle of the Marne. If the French line held, if German advance failed to break through French resistance made on a field long ago selected, prepared, failed to crush French armies now certainly equal and with the Army of Paris superior in numbers, possessing the incal- culable advantage of fighting near its own base of supplies and with a network of railways behind it to enable speedy reenforcement of threatened points, then the whole German offensive must inevitably come to a halt, must presently recoil. For it was not sufficient to hold the French on their present lines. Immediately the necessity of sending more troops eastward would become pressing, and if the German forces in France could not win with the numbers they now possessed, what chance would they have when reduced? In addition the question of their communications would shortly become serious, was in fact now the gravest problem of German com- manders. As for the Allies, defeat would certainly mean a