From 1917: War, Peace, and Revolution, by David Stevenson (OUP Oxford, 2017), Kindle pp. 268-270:
The breakdown of the 1917 peace feelers can be explained at different levels. Certainly it demonstrated the perils of amateur diplomacy. An older Catholic, aristocratic, and dynastic Europe, alongside the socialists and portions of the business elite, attempted to transcend divisions, as later it would support continental unification. Yet mediators such as Sixte and the Coppées helped sustain the contacts by over-representing to each party the other’s goodwill, and it is hard to see that professionals would have done better. Although the feelers made both sides review their war aims, they remained far apart. Admittedly, there were signs of movement: some French and British leaders were prepared at least to talk to the Germans; and the Germans to renounce the annexation of Longwy-Briey and give up the Belgian coast, while the Austrians considered ceding the Italian-majority areas of the Trentino (though both Central Powers hoped for compensations). But the Allies were less willing to jettison their claims. The British wanted full restoration for Belgium and to retain Germany’s colonies, while the German leaders, except for Kühlmann and briefly Bethmann, insisted on continuing control of Belgium. Nor would they cede more than a fraction of the Alsace-Lorraine of 1870, whereas the French wanted all of it, and preferably more. Italy’s Treaty of London claims on Austro-Hungarian territory were an equally formidable stumbling block. The territorial controversies really mattered, for economic and strategic reasons as well as on grounds of national self-determination, ethnicity, and international law and morality. But behind the territorial disputes lay a deeper issue: that the peace feelers served as weapons in the struggle, and especially to divide the enemy. The British and French saw the Sixte and Armand–Revertera affairs as such opportunities, as did Kühlmann the Villalobar contact. Both alliances’ efforts to shatter the other had been central to pre-1914 diplomacy, and this quest continued during the war.
The belligerent governments were cognizant of the rising threat of revolution and Czernin tried to use it as a lever. But none, except for Russia, stood quite yet on the verge of insurrection. Socialist and labour movements had gained support, but a renewed and strident nationalism rallied against them, and governmental concessions to the Left—such as pledges to support a League of Nations—were cosmetic. The domestic balance in the major belligerents shifted in favour of anti-war forces, but not, until the Bolsheviks seized power, by enough to end the conflict. The Reichstag peace resolution meant less than it seemed. Moreover, if the diplomatic and domestic political elements in Europe’s stalemate softened rather than dissolved, the same was true of the military deadlock. By summer 1917 both unrestricted submarine warfare and the Allies’ Chantilly offensives had failed to deliver. But by the autumn Russia’s collapse opened new prospects for the Central Powers, especially in conjunction with tactical innovations that brought renewed successes for their armies. And conversely America’s deepening engagement gave the Allies reason to hope that time still favoured them. Ribot and Lloyd George gambled on victory coming with American aid, and that in spite of Wilson’s palpable aloofness the Allies could still attain their objectives. It is surprising how little America featured in the 1917 debates, but without it Britain, France, and Italy would most likely have been forced, at best, into the unfavourable compromise that they dreaded. Wilson not only gave them economic, maritime, and psychological support, but also diplomatic backing, by rejecting the Stockholm conference and the papal peace note. For Wilson, too, had decided not to settle for a peace based on the pre-1914 status quo ante, and American power would be applied to forestall one. In the coming winter Washington would assert its leadership of the anti-German coalition. Before considering that development, we must explore the wider world, and the spreading shock waves from the European strife.