Grand Duke Nikolai Nikolaevich Romanov (1856-1929) was a key figure in late Imperial Russia, and one of its foremost soldiers. At the outbreak of World War I, his cousin, Tsar Nicholas II, appointed him Supreme Commander of the Russian Army. From 1914 to 1915, and then again briefly in 1917, he was commander of the largest army in the world in the greatest war the world had ever seen. His appointment reflected the fact that he was perhaps...