NATO Secretary General Jens Stoltenberg declared: "We stand in solidarity with Turkey and support the territorial integrity of our NATO ally, Turkey." US President Barack Obama called his Turkish counterpart, Recep Tayyip Erdogan, to assure him that the United States supported Turkey's right to defend its sovereignty. But privately, they must have been cursing Erdogan. They know what he's up to.

This is the first time in more than 50 years that a NATO plane has shot down a Russian plane, and it happened in very suspicious circumstances.

Even if Turkish radar data is to be believed, the two Russian SU-24s crossed only the bottom of a very narrow appendix of Turkish territory that dangles down into Syria. As Russian President Vladimir Putin said: "Our pilots, planes did not threaten Turkish territory in any way. " What harm could they have done in 17 seconds?

Moreover, the two Turkish F-16s that brought one of the Russian planes down had only 17 seconds to get into position to fire their air-to-air missiles over Turkish territory. It would have been hard to do, in that confined space, without crossing into Syrian territory themselves.

According to the Russian radar data, it was the Turkish planes that crossed into Syrian territory. In this version of the story, the Russian planes were following a well-established route just south of the Turkish border, probably turning into a bomb run against Syrian rebels in Latakia province. How strange that there was a Turkish TV crew in northern Syria, positioned just right to film the incident. (The Russian plane crashed four kilometres inside Syria.)

Either way, it seems quite clear that Erdogan really wanted to shoot down a Russian aircraft, and that the Turkish pilots were under orders to do so if they could find even the slightest pretext. So why would Erdogan want to do that?

Putin said bitterly that Erdogan and his colleagues were "accomplices of terrorists". That's hard to deny: Erdogan is so eager to see Syria's President, Bashar al-Assad, overthrown that he left the Turkish-Syrian border open for four years so that recruits and supplies could reach the Syrian rebel groups, notably including Islamic State.

Putin also observed that: "We have long been recording the movement of a large amount of oil and petroleum products to Turkey from IS-occupied territories. This explains the significant funding the terrorists are receiving."

Black-market oil is IS's largest source of revenue, and almost all of it goes to Turkey – which could not happen without the Turkish government's active connivance. And when the Nusra Front, al-Qaeda's affiliate in Syria, was driving Assad's forces back in north-western Syria last spring, Turkey jammed the Syrian army's telecommunications to help the rebels win.

Erdogan is utterly determined that Assad must go, and he doesn't really care if Assad's successors are Islamist extremists. But he also wants to ensure that there is no new Kurdish state on Turkey's southern border.

That is a problem for him, because that state already exists in embryo. It is called Rojava, a territory that the Syrian Kurds have carved out in the far north of the country along the Turkish border, mainly by fighting IS. Indeed, the Syrian Kurds are the US-led coalition's only effective ally on the ground against IS.

When Erdogan committed the Turkish air force to the Syrian war in July, he explained it to the United States as a decision to fight against IS, but in fact Turkey has made only a token handful of strikes against IS. Almost all Erdogan's bombs have actually fallen on the Turkish Kurds of the PKK (who had been observing a ceasefire with the Turkish government for the past four years), and above all on the Syrian Kurds.

Erdogan has two goals: to ensure the destruction of Assad's regime, and to prevent the creation of a new Kurdish state in Syria. He was making some progress on both objectives – and then along came the Russians in September and saved the Syrian army from defeat, at least for the moment.

Worse yet, Putin's strategy turns out to quite pragmatic, and even rather attractive to the United States despite all the ritual anti-Russian propaganda emitted by Washington. Putin wants a ceasefire in Syria that will leave everybody where they are now – except IS, which they can all then concentrate on destroying.

This strategy is now making some headway in the Vienna ceasefire talks, but it is utterly abhorrent to Erdogan because it would leave Assad in power in Damascus, and give the Syrian Kurds time to consolidate their new state. How can he derail this Russian-led project?

Well, he could shoot down a Russian plane, and try to get a confrontation going between Russia and NATO.

Gwynne Dyer is an independent journalist whose articles are published in 45 countries.