The Brusilov offensive, also known as the June advance, or Battle of Galicia-Volhynia, 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. The victory contributed to a morale upsurge among the Russian troops. The offensive's success led Russia's allies to reconsider their positions on postwar territorial concessions, including the status of Anatolia and the Bosphorus Strait.