Eastern Front (World War I)

The Eastern Front or Eastern Theater of World War I (German: Ostfront; Romanian: Frontul de răsărit; Russian: Восточный фронт, romanized: Vostochny front) was a theater of operations that encompassed at its greatest extent the entire frontier between Russia and Romania on one side and Austria-Hungary, Bulgaria, the Ottoman Empire, and Germany on the other. It ranged from the Baltic Sea in the north to the Black Sea in the south, involved most of Eastern Europe, and stretched deep into Central Europe. The term contrasts with the Western Front, which was being fought in Belgium and France.

During 1910, Russian General Yuri Danilov developed "Plan 19" under which four armies would invade East Prussia. This plan was criticised as Austria-Hungary could be a greater threat than the German Empire. So instead of four armies invading East Prussia, the Russians planned to send two armies to East Prussia, and two armies to defend against Austro-Hungarian forces invading from Galicia. In the opening months of the war, the Imperial Russian Army attempted an invasion of eastern Prussia in the Northwestern theater, only to be beaten back by Germany after some initial success. At the same time, in the south, they successfully invaded Galicia, defeating the Austro-Hungarian forces there. In Russian Poland, the Germans failed to take Warsaw. But by 1915, the German and Austro-Hungarian forces were on the advance, dealing the Russians heavy casualties in Galicia and in Poland, forcing them to retreat. Grand Duke Nicholas was sacked from his position as the commander-in-chief and replaced by Tsar Nicholas himself. Several offensives against the Germans in 1916 failed, including the Lake Naroch Offensive and the Baranovichi Offensive. However, General Aleksei Brusilov oversaw a highly successful operation against Austria-Hungary that became known as the Brusilov offensive, which saw the Russian Army make large gains. Being the largest and most lethal offensive of World War I, the effects of the Brusilov offensive were far reaching. It helped to relieve the German pressure during the Battle of Verdun, while also helping to relieve the Austro-Hungarian pressure on the Italians. As a result, the Austro-Hungarian Armed Forces were fatally weakened, and finally Romania decided to enter the war on the side of the Allies. However, the Russian human and material losses also greatly contributed to the Russian Revolutions.

Romania entered the war in August 1916. The Allied Powers promised the region of Transylvania (which was part of Austria-Hungary) in return for Romanian support. The Romanian Army invaded Transylvania and had initial successes, but was forced to stop and was pushed back by the Germans and Austro-Hungarians when Bulgaria attacked them from the south. Meanwhile, a revolution occurred in Russia in March 1917 (one of the causes being the hardships of the war). Tsar Nicholas II was forced to abdicate and a Russian Provisional Government was founded, with Georgy Lvov as its first leader, who was eventually replaced by Alexander Kerensky.

The newly formed Russian Republic continued to fight the war alongside Romania and the rest of the Entente in desultory fashion. It was overthrown by the Bolsheviks in November 1917. Following the Armistice of Focșani between Romania and the Central Powers, Romania also signed a peace treaty with the Central Powers on 7 May 1918, however it was canceled by Romania on 10 November 1918. The new government established by the Bolsheviks signed the Treaty of Brest-Litovsk with the Central Powers in March 1918, taking it out of the war; leading to a Central Powers victory on the Eastern Front and Russian defeat in World War I.