After graduation from the
Nicholas School of Military Engineering (Nikolaevskoe Inzhenernoe Uchilishche) in 1882, Zayonchkovsky served in the 5th Sapper Battalion. In 1888 he graduated from the
General Staff Academy and served in various staff positions. During the
Russo-Japanese War he commanded the 85th Vyborg Infantry Regiment and the 2nd brigade of the 3rd Siberian Infantry Division. During
World War I Zayonchkovsky commanded first the 30th Army Corps. Following Romania's entry into the war on 27 August 1916, he commanded the
Russian-Romanian Dobruja Army in charge of defending Dobruja against the Central Powers. He was relieved by general
Dmitry Shcherbachev in April 1917 and was in retirement by the time of the
October Revolution. In 1918 he joined the
Red Army, serving in various staff positions. After the end of the
Russian Civil War he switched to teaching in the
Red Army Military Academy and writing. He wrote a two-volume overview of World War I military operations. While a professor, "Zayonchkovsky worked as an agent for the Soviet secret police at the same time he was head of the conspiratorial anti-Bolshevik Monarchist Union (The
Trust)." ==References==