The Brusilov offensive, also known as the "June advance", of June to September 1916 was the Russian Empire's greatest feat of arms during World War I, and among the most lethal offensives in world history. The historian Graydon Tunstall called the Brusilov offensive the worst crisis of World War I for Austria-Hungary and the Triple Entente's greatest victory, but it came at a tremendous loss of life. It was arguably the most successful offensive in the entirety of the First World War. The victory contributed to a moral upsurge among the Russian troops, in 1917, Nicholas II planned a general general offensive along the entire front in order to end the Central Powers. After the victory, the Petrograd conference was held at which the post-war structure of the world was discussed.

The Eastern Front or Eastern Theater of World War I 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.