Today there are more Islamist terrorists around the world than there were on September 11, 2001. John Hannah argues that this statistic alone speaks to the failure of American efforts to wage a war of ideas alongside that on the battlefield. To do so effectively, he argues, Washington must exert pressure on those countries that have sowed the ideas that have given rise to al-Qaeda and Islamic State—including Iran, Turkey, and Qatar, but also friendlier nations:

One important example concerns what President Trump discussed in Riyadh back in 2017: the need for America’s Muslim partners to take the lead in defeating the ideology of Islamist extremism. Or more importantly, the need for a handful of states, first and foremost Saudi Arabia, to get out of the business of exporting supremacist versions of the faith around the world. Yet you’d be hard-pressed to find Trump ever speaking publicly about the issue again. Instead, his demands on the Saudis rapidly shifted to shorter-term, more transactional issues like buying ever-greater quantities of U.S. weapons, keeping oil prices low, and supporting what in all likelihood will be a stillborn plan for Middle East peace. . . .

That’s particularly unfortunate, because the Saudi crown prince Mohammad bin Salman has himself claimed since late 2017 that Riyadh is now determined to destroy the extremist ideology that it did so much, for so long, to promote. To the crown prince’s credit, it hasn’t all been lip service. [For instance, the Saudi-based] Muslim World League’s . . . head, Mohammad al-Issa, a cleric and former justice minister, has made a series of remarkable statements in what appears to be a sincere one-man campaign to promote moderation—including condemning Holocaust denial, promising to visit Auschwitz, and telling Muslim minority communities to “embrace the nations they live in,” strictly obey national laws, and positively integrate into society. . . .

But Wahhabism’s trail of wreckage runs deep and wide. It will take much more than a few op-eds by a single Saudi cleric to make a dent in the damage that’s been done.

Last month, two potent reminders were on vivid display. In the run-up to Indonesia’s national elections, several reports detailed the troubling expansion of Saudi-backed Wahhabism in the world’s most populous Muslim-majority country. . . . And in the aftermath of the Easter attacks in Sri Lanka, article after article described the inroads that Wahhabism had made over decades, generating serious fractures within Sri Lanka’s Muslim community and establishing a fertile breeding ground for the kind of violent extremists who perpetrated the bombings.

Two extraordinary events demonstrate something important about Israel’s most fervent adversaries. One was a speech given at something called The People’s Forum (funded generously by Goldman Sachs), which stated, “When the state of Israel is finally destroyed and erased from history, that will be the single most important blow we can give to destroying capitalism and imperialism.”

The suggestion that this tiny state is the linchpin of a global, centuries-old phenomenon like capitalism goes well beyond anything resembling rational criticism. Even if Israel were guilty of genocide, apartheid, and oppression—which of course it is not—it would not follow that its destruction would help end capitalism or imperialism.

The other was an anti-Israel protest that took place in front of New York City’s Memorial Sloan Kettering Cancer Center, deemed “complicit” in Israel’s evils. At organizers’ urging, participants shouted their slogans at kids in the cancer ward, who were watching from the windows. Given Hamas’s indifference toward the lives of Gazan children, such callousness toward non-Palestinian children from Hamas’s Western allies shouldn’t be surprising. The protest—like the abovementioned speech—deliberately conveyed the message that Israel is the ultimate evil and its destruction the ultimate good, cancer patients be damned.

The fact that Israel’s adversaries are almost comically perverse does not mean that they can be dismissed. If its allies fail to understand the obsessive and irrational hatred that it faces, they cannot effectively help it defend itself.