Grand Duke Nikolai Mikhailovich is the author of many historical works dedicated to the era of Alexander I and the Napoleonic Wars. "Emperor Alexander I. Experience of Historical Research" in two volumes (in French. St. Petersburg, 1912. 2nd ed., 1914) - the most fundamental of them. Despite the abundance of historical literature about the era of Alexander I, this book was a new word in science. Its novelty was that Nikolai Mikhailovich used many previously inaccessible materials stored in secret state archives, for the use of which only the emperor could give permission.