There were certain factors which even at the zenith of Germany's fortunes may have prepared a cool-headed critic for a swing of the scales, though the wisest and best informed could not have conceived how violent the oscillation would be. In the first place, the ever-pressing strangle-hold of the Navy, combined with an indifferent harvest and the exhaustion of certain stocks within the Empire, notably of copper, rubber, wool, and lubricants, produced great internal difficulties which grew worse with every month. Then again German successes had been bought in reckless fashion at a very heavy price, and if they brought a million men across from the Russian frontier it is probable that they had squandered nearly as many in the three great battles. Finally, there was the all-important factor of the American reinforcements which had been speeded up to meet the pressing emergency. By splendid international co-operation the Americans put all their proverbial energy into marshalling and equipping the men, while Great Britain threw every available unit of her sea power, mercantile or naval, into the task of getting them across. The long-suffering people of this island gladly cut down their requirements in every possible direction so as to secure the tonnage for this marvellous transfer. At a steady rate of a quarter of a million every month the Americans flowed into France--magnificent raw material which was soon to show how quickly it could develop into the most highly finished article. {3} This constant addition to the Allied forces, with the moral confidence which they brought with them, was the third contributory cause to the sudden change of fortune. It would be ungenerous, however, not to add that a fourth, without which all others might have been vain, lay in the commanding personality and extraordinary genius of the great Frenchman who now controlled the whole Allied battle front from the sea to the Alps, while two great civilians, Lloyd George and Clemenceau, rallied the home fronts of the two weary nations which had borne the brunt of the war.