By 1917, the need for manpower to sustain Allied formations became increasingly important as events unfolded on both the Western and Eastern Fronts. By the close of 1917, the Allies faced numerous and immediate strategic and operational problems. Unrestricted German submarine warfare wreaked havoc on trans-Atlantic supply lines. Reinforcements were dwindling; manpower in Allied forces was shrinking and there were increasing numbers of deserters from the French Army. Although the United States entered the war on 6 April 1917, and had the potential to tip the scales in favour of the Allies, it would be months before a significant field force was ready for deployment. Britain, the Dominions and France continued to shoulder the weight of the war. In addition, after the disaster at Caporetto in October to November 1917, the Italians were struggling to maintain a professional field force. Moreover, there was no Allied breakthrough on the Western Front and stalemate and attrition continued.

To compound the Allies’ problems, they witnessed the capitulation of their Russian ally and the collapse of the Eastern Front in November 1917. From mid-1917, the Germans began to relocate men and materials to the Western Front in preparation for a massive offensive. By the time the Treaty of Brest-Litovsk was signed on 3 March 1918, forty-four German divisions had already been relocated. Between November 1917 and 21 March 1918, when the Kaiserschlacht offensive began, the Central Powers had increased their fighting strength on the Western Front by 30 per cent. By comparison, Allied strength fell by 25 per cent over the same period, the result of the devastating losses sustained during the Passchendaele offensive and the dearth of immediate replacements.