While the Western Front had reached stalemate, the war continued in East Europe. Initial Russian plans called for simultaneous invasions of Austrian Galicia and German East Prussia. Although Russia's initial advance into Galicia was largely successful, they were driven back from East Prussia by Hindenburg and Ludendorff at Tannenberg and the Masurian Lakes in August and September 1914. Russia's less developed industrial base and ineffective military leadership was instrumental in the events that unfolded. By the spring of 1915, the Russians had retreated into Galicia, and in May the Central Powers achieved a remarkable breakthrough on Poland's southern frontiers. On 5 August they captured Warsaw and forced the Russians to withdraw from Poland.
Despite the success of the June 1916 Brusilov Offensive in eastern Galicia,dissatisfaction with the Russian government's conduct of the war grew. The success was undermined by the reluctance of other generals to commit their forces to support the victory. Allied and Russian forces were revived only temporarily with Romania's entry into the war on 27 August. German forces came to the aid of embattled Austro-Hungarian units in Transylvania and Bucharest fell to the Central Powers on 6 December. Meanwhile, unrest grew in Russia, as the Tsar remained at the front. Empress Alexandra's increasingly incompetent rule drew protests and resulted in the murder of her favourite, Rasputin, at the end of 1916.
In March 1917, demonstrations in Petrograd culminated in the abdication of Tsar Nicholas II and the appointment of a weak Provisional Government which shared power with thePetrograd Soviet socialists. This arrangement led to confusion and chaos both at the front and at home. The army became increasingly ineffective.
The war and the government became increasingly unpopular. Discontent led to a rise in popularity of the Bolshevik party, led by Vladimir Lenin. He promised to pull Russia out of the war and was able to gain power. The triumph of the Bolsheviks in November was followed in December by an armistice and negotiations with Germany. At first the Bolsheviks refused the German terms, but when Germany resumed the war and marched across Ukraine with impunity, the new government acceded to the Treaty of Brest-Litovsk on 3 March 1918. It took Russia out of the war and ceded vast territories, including Finland, the Baltic provinces, parts of Poland and Ukraine to the Central Powers. The manpower required for German occupation of former Russian territory may have contributed to the failure of the Spring Offensive, however, and secured relatively little food or other materiel.
With the adoption of the Treaty of Brest-Litovsk, the Entente no longer existed. The Allied powers led a small-scale invasion of Russia, partly to stop Germany from exploiting Russian resources and, to a lesser extent, to support the "Whites" (as opposed to "Reds") in the Russian Civil War. Allied troops landed in Archangel and inVladivostok.