Taking the name Koba, that of a fictional Caucasian bandit-hero (Stalin, or “man of steel,” would come much later), he embarked on a career as an underground political agitator, his life punctuated by multiple arrests and years spent in internal exile. When Stalin, later in life, asked his mother why she had beaten him so much, she replied, “It didn’t do you any harm.” A brilliant but rebellious student at the religious schools he attended, and a published poet of great promise, Soso took up radical politics while still in his teens, his approach already shaped by the tactics of the seminary’s administration - “surveillance, spying, invasion of inner life, violation of feelings,” as he later described them.

Soso, as Stalin, born Josef Djugashvili, was called, suffered savage beatings from both his alcoholic father and his doting mother, who alternated smothering affection with harsh corporal punishment. Montefiore writes, “that rare combination: both ‘intellectual’ and killer.” The roots of violence ran deep in his family life and in Gori, his hometown, where street brawling was the principal sport. Throughout, he connects dots and fills in the blanks, uncovering facts that Stalin, once he assumed power, took great pains to conceal. Montefiore has found his devil in the details, working his way with a fine-toothed comb through previously unread archival material in Russia and in Georgia, where he uncovered a memoir written by Stalin’s mother.

Just as he did in “Stalin: The Court of the Red Tsar,” his lurid, grisly chronicle of Stalin in power, Mr.

No one, henceforth, need ever wonder how it was that Stalin found his way into Lenin’s inner circle, or took his place in the ruling troika that assumed power after the storming of the Winter Palace. Montefiore offers a detailed picture of Stalin’s childhood and youth, his shadowy career as a revolutionary in Georgia and his critical role during the October Revolution. Building on the revisionist studies of Robert Service and Richard Overy, Mr. In “Young Stalin,” Simon Sebag Montefiore’s meticulously researched, authoritative biography of Stalin’s early years, the blur comes into sharp focus.

History, in this case, was written by the losers, notably Leon Trotsky, who never could accept that he had been bested by a pockmarked thug from Georgia with shaky intellectual credentials. He was, in the words of one political adversary, Nikolai Sukhanov, “a gray blur,” a mediocre party hack who managed, through stealth and intrigue, to wrest the levers of power from the brilliant revolutionaries surrounding him. For decades historians accepted the portrait of Stalin painted by his rivals.

Stalin by Simon Sebag Montefiore