ANALYSIS
This is the war Islamic State wants, against squabbling enemies far more suspicious of each other than they are united in a fight against the extremists themselves.
Had Russia and Turkey forged a single goal in this conflict, to destroy Islamic State, the sensitivities of sovereign territory would surely not have mattered, as they don't for the extremists.
Instead, there is now widespread fear of a spiralling war, with a Russian bomber shot down by a Turkish F-16. It came after an apparent territorial violation by the Russian jet, though Russia denies this.
Turkey is a NATO member, and suddenly once vaguely remembered Cold War horrors have rushed back to collective consciousness.
But this is not the Cold War. There will doubtless be plenty of fiery words in the days ahead, yet this act alone - like the US bombing of the Chinese embassy in the 1999 Kosovo war - is unlikely to spark a bigger conflict.
There is even a chance the intense pressure might serve to force all the competing countries to finally negotiate common ground.
Vladimir Putin's immediate response was illustrative, and it is worth highlighting a few key phrases, no doubt deliberately chosen.
Putin branded Turkey's action a "stab in the back" in the fight against Islamic State, but he likely meant more than what had just happened with the downing of the Russian warplane.
Turkey has also directed attacks on Kurdish fighters in Syria, some fighting the Islamists, raising the ire of Western allies.
Seemingly to reinforce the point, Putin frankly acknowledged "I understand that every state has its own regional interests".
But then he urged the international community "to come together and fight against the common evil". In this, the Russian leader is right.
Putin, of course, has done plenty of stabbing of his own in recent months in the ruthless pursuit Russia's interests in Syria.
He is determined to bolster the faltering regime of Bashar al-Assad, a tyrant Turkey would sooner see gone. Most of Russia's airstrikes in Syria are said to have targeted the other opposition groups fighting Assad.
But the defeat of Islamic State should be Putin's principal concern, remembering the other Russian plane destroyed in recent weeks - the commercial airliner destroyed by an Islamic State bomb with more than 220 passengers on board.
