Having presided over mass arrests and executions during the Great Purge, Yezhov eventually fell from Stalin's favour and power. He was arrested, confessed to a range of anti-Soviet activity, later claiming he was tortured into making these confessions, and was executed in 1940.
Yezhov was born either in Saint Petersburg, according to his official Soviet biography, or in Suwałki Governorate of the Congress Poland. In a form filled out in 1921, Yezhov claimed some ability to speak Polish and Lithuanian.
He completed only his elementary education. From 1909 to 1915, he worked as a tailor's assistant and factory worker. From 1915 until 1917, Yezhov served in the Imperial Russian Army. He joined the Bolsheviks on May 5, 1917, in Vitebsk, six months before the October Revolution. During the Russian Civil War, 1919–1921, he fought in the Red Army. After February 1922, he worked in the political system, mostly as a secretary of various regional committees of the Communist Party. In 1927, he was transferred to the Accounting and Distribution Department of the Party where he worked as an instructor and acting head of the department. From 1929 to 1930, he was the Deputy People's Commissar for Agriculture. In November 1930, he was appointed to the Head of several departments of the Communist Party: department of special affairs, department of personnel and department of industry. In 1934, he was elected to the Central Committee of the Communist Party; in the next year he became a secretary of the Central Committee. From February 1935 to March 1939, he was also the Chairman of the Central Commission for Party Control.
In the "Letter of an Old Bolshevik" (1936), written by Boris Nicolaevsky, there is this contemporary description of Yezhov: