From June to August 1916 the Russian forces launched their last major offensive of the war The Brusilov Offensive. initially it was a success, even prompting Romania toenter the war on Russias side, yet by August it had run out of momentum. The Russian forces had to retreat from the Baltic sea to the Black sea. (17h 32min, jun 14, 1916 y – 3h 45min, aug 31, 1916 y)
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Date:
17h 32min, jun 14, 1916 y
3h 45min, aug 31, 1916 y
~ 2 months and 18 days