The Russian Provisional Government had declared a political amnesty that allowed political exiles to return home, notably Leon Trotsky and Vladimir Lenin, who got an assist from the German government.
The US entered the war in early 1917, but it would take time for her to have an impact on the war. Brazil also joined the war in 1917, and in Canada, the political fight over conscription leads to a divisive general election.
By 1917, many in German and Austrian official and military circles had given up hope of winning the Great War on the battlefield and were ready to discuss peace terms. Hindenburg and Ludendorff, however, insisted that victory was at hand.