Allied military plans to win the war in 1917 were derailed by a distracted Russia and by a breakdown of discipline in the ranks of the French army in the wake of Nivelle's debacle. The waning effectiveness of the Russian and French armies made Britain the mainstay of the anti-German coalition. The numerical advantage on which the Entente had counted to wear down the Germans was nullified, at least for the foreseeable future. Britain faced two dangerous choices. If it took on the Germans with only limited help from its European allies, it would bleed to death and be unable to sustain the struggle in the final stages.

The other option was to remain inactive until American forces could be thrown into the scale. But the United States was unprepared to fight in a major war. Both the British and French governments had tried unsuccessfully to urge Washington to permit and encourage the massive enlistment of Americans in their respective armies. For the immediate future, American assistance would be limited to one division. The best estimate in London was that American troops would not be able to assume a large burden of fighting in the land war until late in 1918 or even 1919. Thus, if the Allies remained quiescent in the west, there existed the possibility that the Germans would seize the initiative and finish off Russia or Italy or both, forcing Britain to accept a peace settlement that would deprive it of much of its empire and its status as a first-class power.