When the Allied counteroffensive forced German forces to retreat behind the Hindenburg Line on 2 September 1918, the writing was on the wall for the Central Powers. By the end of the month, the Line had been breached and Bulgaria had surrendered to the Allies. In October, the German navy mutinied at Kiel, and Italy steamrollered the demoralized Austro-Hungarian army after the Battle of Vittorio Veneto, matched by the Serbians marching on the empire from the south. With the Balkans lost, Germany was effectively without supplies of both oil and grain. German puppet states created in former Russian territory after the Treaty of Brest-Litovsk began to break away. When, in mid-October, the US upheld its doctrine of national self-determination in relation to Austria-Hungary, Czech, Hungarian and South Slavic declarations of independence swiftly followed. On 30 October, the Ottoman Empire ended their war with the Armistice of Mudros.
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