According to legend, Troy fell in part because it did not heed the warnings of Cassandra. The daughter of King Priam, the myth goes, had been blessed by Apollo with the gift of prophecy — and then cursed by him after she rejected his advances. Her fate: No one would ever believe her prophecies again. Cassandra is sometimes credited with offering the unheeded advice, "Beware of Greeks bearing gifts," after trying to stop Troy from bringing in the large wooden horse that Agamemnon used as a trap to sack the city. And from this legend we get the Cassandra Syndrome, where prophets who issue accurate warnings of doom get ignored due to some fatal flaw in their credibility.

And that brings us to Tony Blair. Blair started off his run as prime minister of the U.K. as a modernizing figure, but spent the last half of his term defining himself as a wartime leader partnered with George W. Bush in Iraq. Unlike Bush, who has remained silent on national-security issues since his retirement, Blair continues to defend the U.S.-U.K. partnership on the 2003 invasion of Iraq, and the need for a forward strategy against Islamist terror. Needless to say, the Iraq misadventure has long frustrated his former Labour base in the U.K., and poked big holes in Blair's credibility on Middle East policy.

But the events of the last several months have validated Blair's warnings about the danger of withdrawal and disengagement in Iraq. And now, Blair is back in the prophecy business. In a lengthy essay published by his foundation, Blair warned the West that its strategy of conducting airstrikes alone on ISIS would not suffice in ending the threat to the region. "Airpower is a major component" of a successful long-term strategy, Blair wrote, but the "hard truth" is that ISIS "can't be defeated by it." Blair acknowledged that, thanks in no small part to the war which he helped lead, the West has no appetite for another lengthy ground engagement, and he himself rejects the idea of another extended occupation. The only way to truly defeat ISIS, he said, will be to take away the land they control, and if the only way to do that is the use of Western ground troops as part of "the broadest achievable alliance" and with "the consent of the population directly threatened," then the West "should not rule [ground troops] out in the future."

Blair's advice will surely not be welcomed by the Powers That Be in Washington D.C., London, Brussels, or practically anywhere else. Opponents will accuse Blair of offering unsolicited and ill-advised solutions to chaos he created himself (along with Bush), rather than criticize the post-Blair retreat by the U.S. and U.K. from policies of continued military engagement. But spin aside, let's go ahead and just test Blair's prophecy on air power. According to The New York Times, it hasn't had anywhere near the ISIS-degrading impact promised by President Obama. "After six weeks of American airstrikes," David Kirkpatrick writes, "the Iraqi government's forces have scarcely budged Sunni extremists of the Islamic State from their hold on more than a quarter of the country."

We can blame, at least in part, the lack of participation against ISIS on the ground by Sunni tribes. Those tribes once backed the U.S. in the fight against ISIS's predecessor organization, al Qaeda in Iraq, when Bush put the "surge" into effect and committed to the fight against the terrorist network, while reassuring the Sunni tribal leaders that the U.S. would commit to ensuring their participation in Iraqi self-government. Our withdrawal taught them a lesson about the squishiness of American promises, and it's not surprising that a few weeks of airstrikes wouldn't change their long-term forecasts about the balance of power in the region. Kirkpatrick reports that they aren't much more impressed with new Prime Minister Haider al-Abadi than they were with Nouri al-Maliki, and want a completely new, non-sectarian "technocrat" government instead.

So the airstrikes in Iraq haven't budged ISIS from its positions, and don't seem to have helped much yet in Syria, either. And that means that at least so far, Blair has been proven correct. Air power alone will not roll back ISIS.

Blair's larger issue is that the West hesitates to confront extreme Islamism, and not just the fringe groups in play at the moment. The West has to recognize, Blair urges, that Islamism is a spectrum of thought in the region, and that it is wholly "incompatible with modern economies and open-minded, religiously pluralistic societies."

In places where there is a debate between Islamism and pluralism, Blair writes, "there is a side we should take. And we should do so with energy, because they need our support." Trying to make deals with so-called moderate Islamists — like the Muslim Brotherhood in Egypt — is sheer folly. "We should not make the mistake of dealing with the Muslim Brotherhood as if it were merely an Arab version of the Christian Democrats," Blair writes. "It isn't and there is little sign it ever will be." Pretending that these are neutral-balanced competing value systems will be a fatal mistake, and already has been proven so in Egypt.

This is the larger war the West must fight, a war of enlightenment, ideas, and values as well as an unavoidable military confrontation, both of which need to be engaged broadly — not just tactically when the atrocities mount so high as to defy impassiveness. Blair offers this both as a prophecy of victory in his confidence that the West can get this right, and a warning as to the stakes if we don't. The question will be whether Blair is still cursed as a Cassandra or finally given the consideration due his experience — and his track record.