Less than a year after satirical depictions of the prophet Muhammad in a Danish newspaper sparked a worldwide wave of violence, Muslims throughout the world are up in arms again. This time the rage is focused on the alleged defamation of the prophet by Pope Benedict XVI. His sin: citing an obscure passage from a late-14th-century debate between the Byzantine Emperor Manuel II and a Muslim scholar in which the emperor denounced the Islamic duty of jihad, for whose sake the Ottomans were then besieging Constantinople, as “evil and inhuman.”

It mattered not that Benedict didn’t endorse this indictment or that the quote was marginal to his lecture. The Muslim reaction was swift and violent. Inflamed crowds took to the streets in many countries to protest the supposed defamation. In Gaza and the West Bank a number of churches were attacked, fired at, or set on fire; in Somalia gunmen shot dead an elderly Italian nun, while in Kashmir mobs burnt an effigy of the pontiff. In Turkey, due to host in November Benedict’s first visit to a Muslim country, the ruling party likened the pope to Hitler and Mussolini and accused him of reviving the mentality of the Crusades. Radical clerics have called, variously, for a “day of anger” or for worshipers to “hunt down” the pope and his followers, and an Iraqi militant group announced its intention to murder the pope.

That these acts of violence make a mockery of protestations of Islam’s tolerant spirit has been totally lost on the pope’s critics. And why shouldn’t it? Not only did the Vatican issue a prompt apology in a desperate bid to defuse the unfolding crisis, but in the years since the terrorist attacks of September 11, 2001, a vast cohort of Western apologists has consistently painted a surrealistic picture of Islam’s political agenda. Depicting jihad as an inner quest for personal self-improvement, rather than the “holy war” claimed by countless Muslim dynasties and leaders throughout history, they dismissed the worldwide wave of Islamic terrorism as an excessive reaction by misguided fringe groups to America’s arrogant and self-serving foreign policy. “Muslims have never nurtured dreams of world conquest,” wrote Karen Armstrong, a prominent representative of this view, shortly after September 11. “They had no designs on Europe, for example, even though Europeans imagined that they did. Once Muslim rule had been established in Spain, it was recognized that the empire could not expand indefinitely.”

This assertion couldn’t be further from the truth. Not only was the conquest of Spain, some 2,000 miles from the Arabian homeland, a straightforward act of imperial expansion, it hardly satisfied Islam’s territorial ambitions. No sooner had the Muslims established themselves in that country than they invaded France in strength. Had they not been contained in 732 AD at the famous battle of Poitiers in west central France, they might well have swept deep into northern Europe.

Unperturbed by this historical record, Ms. Armstrong is making a fresh attempt to validate the “Islam equals peace” thesis. “Muhammad: A Prophet for Our Time” (HarperCollins, 235 pages, $21.95), is a thinly veiled hagiography, depicting the prophet as a quintessential man of peace, “whose aim was peace and practical compassion” and who “literally sweated with the effort to bring peace to war-torn Arabia”; an altruistic social reformer of modest political ambitions, whose life was “a tireless campaign against greed, injustice, and arrogance” and who founded “a religion and cultural tradition that was not based on the sword but whose name — ‘Islam’ — signified peace and reconciliation.”

In truth, Islam’s actual meaning is submission and not peace, or to use Ms. Armstrong’s own words, “the perfect surrender (in Arabic the word for ‘surrender’ is islam) that every human being should make to the divine.” And it was to achieve this goal and subordinate the Arabian peninsula to his rule that Muhammad fought almost incessantly for the last 10 years of his life, having fled from his hometown of Mecca to Medina in 622 to become a political and military leader rather than a private preacher: not to bring peace to a war-torn country, let alone to eliminate “greed, injustice, and arrogance.”

In contrast to Ms. Armstrong’s depiction of jihad as a benign struggle for self-improvement, the Qur’anic revelations during Muhammad’s Medina years abound with verses extolling the virtues of fighting “in the path of Allah,” as do the countless sayings and traditions (hadith) attributed to the prophet. As he told his followers in his farewell address: “I was ordered to fight all men until they say ‘There is no god but Allah.'” Had it not been for his sudden death, Muhammad probably would have expanded his control well beyond the peninsula.

Ms. Armstrong goes out of her way to whitewash Muhammad’s extermination of the Jewish presence in Medina, especially the beheading of the entire 600 to 800 male population of the Qurayzah tribe. “[T]he Qurayzah were not killed on religious or racial ground,” she claims, adding that “Muhammad had no ideological quarrel with the Jewish people.” This is of course a travesty of the truth. Muhammad might have had no ideological quarrel with “the Jewish people,” but he was seething with anger at the Medina Jews, who had not only spurned his attempts to woo them into his incipient religion (for example, by adopting a number of religious Jewish practices and rituals) but had also become his fiercest critics. Reflecting this outrage, both the Qur’an and later biographical traditions of the prophet abound with negative depictions of Jews. In these works they are portrayed as a deceitful, evil, and treacherous people who in their insatiable urge for domination would readily betray an ally and swindle a non-Jew.

Ms. Armstrong glibly claims that “Later in the Islamic empires, Jews would enjoy full religious liberty and anti-Semitism would not become a Muslim vice until the Arab/Israeli conflict became acute in the mid-twentieth century.” For one thing, such ahistorical analysis ignores the deep anti-Jewish bigotry dating to Islam’s earliest days, which made it highly receptive to the worst precepts of Christian anti-Semitism, such as the “blood libel.” For another thing, Armstrong overlooks Islam’s pervasive mistreatment of its non-Muslim subjects, or Dhimmis as they are commonly known, who have been allowed to practice their religions in return for a distinctly inferior legal and institutional status, rife with social indignities and at times open persecution.

“If we are to avoid catastrophe, the Muslim and Western worlds must learn not merely to tolerate but to appreciate one another,” Ms. Armstrong emphatically concludes her book. I couldn’t agree more. Provided of course this is done in good faith and without rewriting the historical truth, let alone violently suppressing critical minds and dissenting voices.

Mr. Karsh is head of Mediterranean Studies at King’s College, University of London, and author most recently of “Islamic Imperialism: A History,” available from Yale University Press.