Leon Trotsky was both an intellectual and a man of action. One of the charismatic leaders of the Russian Revolution—Lenin said there was no better Bolshevik—he created the Red Army through virtually an act of will and led it to victory in the 1918-20 civil war. But he was also a mesmerizing dissenter, sent by Stalin into exile in 1927 and then murdered in Mexico by one of Stalin's agents in 1940.

Trotsky was Jewish—born Lev Davidovich Bronstein in 1879—and it is as such that he is treated in Joshua Rubenstein's brief biography, part of Yale University Press's Jewish Lives series. Trotsky said that his ethnic background had not the slightest influence on his life. But no one inquiring into his origins can ignore what it meant to be a Jew in a Russia permeated with anti-Semitism or can suppose that because Trotsky opposed Zionism—or, indeed, any movement or policy that favored Jews—he was unaffected when many of his actions were attributed to his Jewishness.

Isaac Deutscher, the author of the classic biography of Trotsky (three volumes, published between 1954 and 1963), largely took his subject at his word, noting only those instances when Trotsky himself raised the issue of his Jewishness. Trotsky rejected, for example, Lenin's wish to appoint him commissar of home affairs in 1917, pointing out, according to Deutscher, that counter-revolutionaries would "whip up anti-Semitic feeling and turn it against the Bolsheviks." After Lenin died in 1924, Trotsky appealed to Nicolai Bukharin, a fellow Politburo member, to speak out against the anti-Semitic Party members working for Stalin who had begun "hinting" (Deutscher's word) that Trotsky had better give way to "native and genuine Russian socialism." Otherwise, Deutscher is as silent as his subject about the nexus between "Trotsky and the Jews."

That is the title of a chapter in Robert Service's "Trotsky" (2009), which provides helpful background. Trotsky was not a so-called self-hating Jew. He often lived among Jews in Russia and abroad, but he described himself as an "internationalist," which meant that he wanted nothing whatever to do with specifically Jewish causes. He neither favored nor discriminated against Jews and spoke up for them only in terms of his defense of all minorities suffering discrimination.

Mr. Service, however, clarifies an aspect of Trotsky's belief and behavior that bears directly on what Mr. Rubenstein calls Trotsky's "curiously passive" stance during the period after Lenin's death, when Stalin was busily lining up allies and consolidating his hold on power. Mr. Service observes: "Trotsky continued to believe that his own prominence in government, party and army did practical damage to the revolutionary cause." Surprisingly, Mr. Rubenstein, who is highly critical of Mr. Service's biography for its "gratuitous criticism of Trotsky's character and personality" and its failure "to understand the full complexity of Trotsky's relationship to his Jewish origin," does less in a whole book than Mr. Service did in that single sentence to explain why it was—with the fate of a revolution in his hands, with at least the chance to outwit and even outgun Stalin—Trotsky hesitated and so lost. (He also underestimated his opponent, thinking that because Stalin had neither his intellect nor experience, he would fail.)

To put it another way, Mr. Rubenstein's Trotsky is not Jewish enough. Like Deutscher, he seems beguiled by Trotsky's own denials. In one sense, this accession is understandable. How can the biographer say being a Jew was important to Trotsky when Trotsky's public pronouncements and actions—and even his private behavior—seem devoid of any sort of Jewish resonance. To harp on his Jewishness, to endow it with special qualities, would play into the most anti-Semitic notions of Jewishness. But though Trotsky never tired of saying "I'm no Jew, I'm an internationalist," he knew very well that nothing would change ingrained prejudices. And so knowledge of his Jewishness affected his decisions at the most important moment of his career.

Although Mr. Rubenstein conscientiously describes Trotsky's dealings with Jews and Jewish issues, he is wary of attributing any feelings and motivations about Trotsky's ethnicity to Trotsky himself. He never mentions it in analyzing Trotsky's downfall, for instance, though this is ascribed to many factors: Trotsky's early opposition to Lenin, which many Bolsheviks could not forgive; Trotsky's independent and outspoken attitudes, which, mixed with contempt for his rivals, made it difficult for him to secure allies; Trotsky's refusal to act as ruthlessly as his opponent; the strange and seemingly psychosomatic fevers that felled Trotsky at critical moments; and Trotsky's absolute faith in the authority of the party that was in the vanguard of history and his countervailing lack of faith in individuals.

These are all reason enough for Trotsky's decisive failure, and they have been carefully canvassed in the many other Trotsky biographies. And yet a biographer charged with looking at a single issue and how it played out in Trotsky's life might just want to exercise a little boldness, not refuting the multiple reasons for Trotsky's failure to seize power but suffusing them with the underlying premise that, in the eyes of so many others, once a Jew, always a Jew—as Trotsky himself knew full well.

Only once does Mr. Rubenstein seem to recognize Trotsky's lifelong plight. The biographer recounts his subject's response to the case of Mendel Beilis, a brick-factory worker accused of murdering a 12-year-old boy in Kiev in 1912, supposedly to use the blood to prepare matzoh for the Passover holiday—the old blood libel. The trumped-up charges and trial gave rise to world-wide protests and were treated by Trotsky as a czarist effort to stir up anti-Semitism (always a useful outlet for discontent).

Trotsky wrote extensively about the trial (unmentioned in the Deutscher or Service biographies), not merely denouncing it but expressing his disgust even after the jury acquitted Beilis. The cautious Mr. Rubenstein notes that Trotsky's commitment to social justice had "several sources," none of which Trotsky attributed to his Jewish upbringing. But then, summing up Trotsky's passionate coverage of both the Beilis case and earlier the oppressed Jewish community in Romania, he adds this, the most important passage in his whole book:

Perhaps he did not think of himself as a Jew in the same way that they were Jews; he was a Marxist, a convinced internationalist, a man who resisted any narrow parochial appeal in the name of a universal, political faith. But he had still been born and raised as a Jew. Perhaps the starkness of their lives touched something so deep inside his emotional life that he needed to vomit it out, to disgorge it before it compelled him to see himself in their faces. At moments like these, Leon Trotsky was a Jew in spite of himself.

And I would add: not only at those moments. Just at the moment when Trotsky commanded the world stage and still had time to stop Stalin, he may very well have wondered about doing permanent injury to the revolution he had done so much to bring about by now vouchsafing it to a Jew. As an introduction to Trotsky, Mr. Rubenstein's biography is succinct and reliable. As the last word on Trotsky as Jew, it seems surprisingly reluctant to pick up on the strains in history and in Trotsky's own character that made it impossible for a Jew to command Lenin's legacy. ( )