TONY CENICOLA/THE NEW YORK TIMES

FOR  decades historians accepted the portrait of Stalin painted by his rivals. 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. 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.

In “Young Stalin,” Simon Sebag Montefiore’s meticulously researched, authoritative biography of Stalin’s early years, the blur comes into sharp focus. Building on the revisionist studies of Robert Service and Richard Overy, Mr. 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. 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.

Simon Sebag Montefiore/ Knopf

Just as he did in “Stalin: The Court of the Red Tsar,” his lurid, grisly chronicle of Stalin in power, Mr. 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. Throughout, he connects dots and fills in the blanks, uncovering facts that Stalin, once he assumed power, took great pains to conceal.

No detail is too minute. We learn that Stalin, while living in exile in Vologda in 1911, visited the library 17 times in less than two months. No source, it seems, lies beyond the author’s reach. Mr. Montefiore located a 109-year-old cousin of Stalin’s first wife, Ekaterina Svanidze. Her memory still sharp, Mr. Montefiore’s eyewitness corroborated the assertion, made by other family members, that Ms. Svanidze died in 1907 of typhus, not tuberculosis, as historians mistakenly believed. A small point, but the accretion of direct testimony adds color to the traditional monotone picture of Stalin, bringing him to life on the page.

Stalin was, Mr. 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. 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. 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. 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.

Gaunt and darkly handsome despite the facial scars left by smallpox, and blessed with a beautiful singing voice, Koba enchanted women throughout his young manhood and left several illegitimate children as proof. He had a mesmerizing effect on men as well.

“His style, manners were totally Georgian, yet there was something utterly original, something hard to fathom, both leonine and feline about him,” a Georgian Menshevik wrote of this fascinating political opponent.

Mr. Montefiore sheds new light on Stalin’s wild years as a kind of revolutionary gang leader in the Caucasus, putting him at the center of robberies, kidnappings, arson attacks, extortion schemes and executions of suspected traitors. He makes a very strong case that Stalin burned down the Rothschilds’ refinery warehouse in the oil boom town Batumi in January 1902 and thereafter used this act as leverage in extorting protection money from other oil barons. In addition to agitating among workers and fomenting strikes and riots, Stalin specialized in daring, extremely violent bank heists, whose considerable proceeds helped Lenin finance the Bolshevik Party.

Stalin thrived on violence, subterfuge and dark conspiracy. He fully subscribed to the Leninist ideal of the Marxist revolutionary as a man outside normal society and moral law, a pitiless instrument of the working class. The “black work” that Stalin made his métier became standard operating procedure for the Soviet government. Stalin, like his fellow Bolsheviks, never left the shadow world of spies, double agents and criminal conspiracy.

Mr. Montefiore dismisses, perhaps for good, the theory that Stalin was an agent for the Okhrana, the czarist secret police. He spent far too much time in prison or exile, for one thing. On the occasions when he met with agents, Mr. Montefiore points out, Stalin was receiving rather than giving intelligence.

Stalin won Lenin’s wholehearted approval from the moment they met in 1905. In Lenin’s terms he was, quite clearly, one of the highly desirable “men of action,” rather than one of the “tea-drinkers.”

With time their relationship only deepened. Much to Lenin’s surprise, Stalin submitted a brilliant position paper on party policy toward nationalities within the Russian empire. The killer really was an intellectual, and certainly no bureaucrat. Mr. Montefiore notes, shrewdly, that “everything with Stalin was political, but he worked in an eccentric, structureless, unbureaucratic, almost bohemian style that would not have succeeded in any other government, then or now.” Mr. Montefiore successfully captures “the sheer weird singularity of the man” and the lethal instincts that propelled him to the summit of power. Surrounded by hard, ruthless men, Stalin proved to be the hardest and most ruthless. The hands trained in black work had the strongest grip.

Copyright 2007 The New York Times Company. Reprinted from The New York Times, Book Review, of Sunday, October 21, 2007.