EPA Opinion Erdoğan shoots down Putin Turkey’s dangerous brinkmanship with Russia.

What was Erdoğan thinking? One has to assume that the deliberate downing of a Russian bomber by Turkish fighter jets was no accident, that it was ordered from the top. Otherwise, we would have heard very audible diplomatic apologies from the Turkish side to the Kremlin. Nor would Putin have openly called it a “stab in the back.”

This little knot of what-didn't-happen is revealing in itself. Presumably the Turks could have pretended the whole thing was an accident while assuming that Putin got the message. Instead Ankara chose to make Monday's incident a public rebuke and humiliation for the Kremlin, a palpable act of hostility between nations and, indeed, between power blocs, for Erdoğan quickly called a meeting with NATO brass. So what were his calculations?

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We should understand, first, the leadership style of the two presidents to see how such a confrontation could occur. As many have noted, Putin and Erdoğan have built power in comparable ways, using semi-despotic methods of governance to retain and deploy power unilaterally. This has allowed Putin to invade Georgia and Ukraine while Erdoğan has bombed the Kurds in Syria who are fighting ISIL. In both cases, the stoking of armed conflict in the teeth of global criticism led to consolidation of domestic support.

In Erdoğan's case, such a risky use of Turkish air power also indicates that he has totally overcome any residual resistance from the armed forces to his overweening schemes. Both leaders, too, being free to move according to personal whim, tend to act on personal grudges against foreign leaders: witness Putin's constant reviling of Georgia's former President Saakashvili and Erdoğan's of Assad.

So, the war of nerves between Putin and Erdoğan has become a motive force in itself, despite the potential of severe damage to both countries' interests, not least the budding agreement over a Russian fuel pipeline to Europe via Turkey. No small calculation, this, as it meant the freeing up of Russian oil from its dependence on the supply route through Ukraine which gave Kiev strategic leverage over Moscow.

When Putin ordered Russian bombers into Syria to uphold Assad, Erdoğan clearly drew his own conclusions. The Kremlin didn't care enough about the pipeline to show consideration for Erdoğan's feelings. The more “moderate” Syrian opposition forces first bombed by Russia were precisely those getting open support from Ankara.

Furthermore, Erdoğan must have understood that he couldn't depend on the U.S. or Europe (or NATO) to rein in Putin's 19th century-style Great Game initiatives. Putin in Syria might represent a proxy threat to the West's allies; but the West had sharper preoccupations, whereas it represented a direct and comprehensive threat to Turkey: Russia's emboldening of the Shiite crescent from Tehran to Iraq to Syria fully encircled Turkey's land borders to other Muslim countries. Erdoğan could kiss goodbye to his Neo-Ottoman imperial dreams. And presumably to the kind of massive economic infusions from the Sunni Gulf that have bolstered his domestic standing. Why fund him if he watches lamely as the Shiites build their rival power bloc with Moscow's help?

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Above all, though, recent events around ISIL are the likely trigger for Erdoğan's action. Not merely because he seems to harbor a grudging sympathy for their pro-Sunni contributions, but because he sees a potential regrouping of alliances to focus on eradicating ISIL first. He senses that Europe might soften towards Putin in the joint purpose — and what that might entail. He has incited Sunni religious feeling at home to keep power and now he must stand by it: The Christian bloc looks to be uniting against Turkey in a way that recalls the very Ottoman centuries he yearns to recreate. In this scenario, even Greece and Georgia will shut their doors and isolate Turkey altogether.

So Erdoğan has chosen to test the West's allegiance by the kind of brinkmanship that he has seen Moscow exploit repeatedly. He has demanded from his allies an answer to an ultimately divisive question, one that threatens to reorder the world's alignments for the next 100 or so years: Do you wish to revive the Crusades?

Which is precisely what ISIL is hoping to do.

Melik Kaylan, an Anglo-Turk, is a foreign affairs columnist for Forbes.com and co-author of “The Russia-China Axis: The New Cold War” (Encounter Books, 2014).