When I was in sixth grade, a 1967 copy of The Pageant of World History by Gerald Leinwand came into my possession.  While I learned a great deal from it, the book contains shocking omissions.  Here’s what Leinwand says about the early years of Mussolini:

Mussolini, at one time, had been a socialist, and, as a newspaperman, had written articles favoring the overthrow of capitalism.

All true, but so misleading!  Leinwand makes Mussolini sound like a low-level journalist who happened to be a rank-and-file member of the socialist party.  I didn’t learn the real story for decades, when I discovered the works of A. James Gregor, especially his Young Mussolini and the Intellectual Origins of Fascism.  Fortunately for the sixth-graders of today, Wikipedia has the facts that Leinwand leaves out.  Mussolini wasn’t just another socialist; he was the Lenin of Italy – the leader of the hard-line revolutionary faction.  And Mussolini wasn’t just a “newspaperman”; he was the editor of Avanti!, the official newspaper of the Socialist Party.  By 1910, he…

…was considered to be one of Italy’s most prominent
Socialists. In September 1911, Mussolini participated in a riot, led by
Socialists, against the Italian war in Libya. He bitterly denounced Italy’s “imperialist war” to capture the Libyan capital city of Tripoli, an action that earned him a five-month jail term.  After his release he helped expel from the ranks of the Socialist party two “revisionists” who had supported the war, Ivanoe Bonomi, and Leonida Bissolati. As a result, he was rewarded the editorship of the Socialist Party newspaper Avanti! Under his leadership, its circulation soon rose from 20,000 to 100,000.

Wikipedia’s article on the Italian Socialist Party has more details on Mussolini’s purge of “revisionists”:

At the start of the 20th century, however, the PSI chose not to strongly oppose the governments led by five-time Prime Minister Giovanni Giolitti.
This conciliation with the existing governments and its improving
electoral fortunes helped to establish the PSI as a mainstream Italian
political party by the 1910s.

Despite the party’s improving electoral results, however, the PSI
remained divided into two major branches, the Reformists and the
Maximalists. The Reformists, led by Filippo Turati, were strong mostly in the unions and the parliamentary group. The Maximalists, led by Costantino Lazzari, were affiliated with the London Bureau of socialist groups, an international association of left-wing socialist parties.

In 1912 the Maximalists led by Benito Mussolini prevailed at the party convention and this led to the split of the Italian Reform Socialist Party.

For socialists, of course, Mussolini’s apostasy proves nothing except his supreme evil.  For everyone else, though, Mussolini’s origin story puts his subsequent career in a whole new light.  Outsiders can easily see what insiders deny: The apostate fruit rarely falls far from the orthodox tree. 

Yes, Mussolini realized that socialism plus nationalism had more mass appeal than socialism alone.  Yes, Mussolini realized that socialism would be stronger if it allied with the Church instead of destroying it.  Yes, Mussolini realized that full-fledged mass expropriation of private property would devastate the economy.  And yes, Mussolini realized that the word “socialism” alienated millions of Italians who would otherwise be receptive to his message.  But this doesn’t make Mussolini a radical socialist who betrayed everything he believed in.  It makes him a radical socialist who dropped some peripheral socialist dogmas that stood between him and absolute power.  If he’d kept the socialist label and avoided alliance with Hitler, Mussolini might now be a left-wing icon as big as Che Guevara.