The deal between the US and Turkey which will allow American bombers to use Incirlik airbase while Turkey takes action against Islamic State (Isis) looks stranger and stranger. When first announced over a week ago, US officials spoke triumphantly of the agreement being “a game-changer” in the war against Isis. In fact, the war waged by Turkey in the days since this great American diplomatic success has been almost entirely against the Kurds, at home and abroad.

Turkish jets are pounding sites occupied by the PKK (Kurdistan Workers Party) guerrillas in the Qandil Mountains and other parts of northern Iraq. Inside Turkey, the majority of those detained by the security forces turn out to be Kurdish or left-wing activists and not suspected Isis sympathisers. Prosecutions are threatened against MPs of the largely Kurdish Peoples’ Democratic Party (HDP) which has tirelessly advocated peace between the PKK and the Turkish government. Evidently, the HDP’s offence was to win 13 per cent of the votes in Turkey’s general election on 7 June, thereby depriving President Recep Tayyip Erdogan’s ruling AKP of its parliamentary majority for the first time since 2002.

It is now becoming clear that two crucial parts of the accord were not agreed at the time of the historic announcement. The US Air Force was desperate to get the use of Incirlik, 60 miles from the Syrian border, in order to intensify its bombardment of Isis. American planes currently have to fly long distances from Bahrain, Jordan and an aircraft carrier in the Gulf. The failure of the US air campaign to prevent Isis fighters capturing Ramadi and Palmyra in May intensified the sense of urgency.

At the time of writing, US aircraft have not started using Incirlik and the reason is that Turkey does not want US aircraft using it to launch air strikes in support of the Syrian Kurds who have hitherto been America’s most effective military allies against Isis in Syria. The Syrian Kurdish ruling Democratic Union Party (PYD) and its determined and well-disciplined militia, the People’s Protection Units (YPG), successfully defended the city of Kobani (with US air support) during a 134-day siege by Isis. Since then, the PYD has linked up two of its enclaves just south of the Turkish frontier by capturing the Isis-held border crossing of Tal Abyad. Again the YPG was helped by frequent US air strikes. I was just east of Tal Abyad with the YPG in May, and there was scarcely a moment when I could not hear the sound of US aircraft overhead.

Turkey is now demanding that US planes based at Incirlik not be used in support of the PYD/YPG because they are the Syrian branch of the PKK which Turkey is busy trying to destroy with its own air campaign. But US bombing in Syria has mostly been in support of the YPG in the north-east of the country and against Isis-held oil and gas fields in other provinces. Possibly the US could continue to support the Syrian Kurds with aircraft that don’t operate from Incirlik, but using Turkish bases would be a great advantage. And even the US’s ability to do this is in doubt if, as is intended, its single aircraft carrier in the Gulf, the USS Theodore Roosevelt, pulls out this autumn and is not replaced for several months.

Even if this dispute is ultimately resolved, it highlights the contradiction at the heart of US policy: Washington is teaming up with a Turkish government whose prime objective in Syria is to prevent the further expansion of PYD/YPG territory which already extends along 250 miles of the 550-mile-long Syrian-Turkish border. In brief, Ankara’s objective is the precise opposite of Washington’s and little different from that of Isis, which has been battling on the ground to hold back the PYD/YPG advance.

A second point of difference between the US and Turkey is over a plan to establish an Isis-free zone in an area between the Turkish border and Aleppo. This would close off Isis from Turkey, but who is to do it? Turkey says it is not going to commit ground troops. Public opinion in the US would likewise veto American involvement on the ground so its military pressure on Isis must entirely depend on its air power. The Turks and their allies in Saudi Arabia and Qatar would like to rebrand the Jabhat al-Nusra and Ahrar al-Sham, movements, whose beliefs and actions differ little from Isis, as born-again moderates. Jabhat al-Nusra, founded by Isis leader Abu Baqr al-Baghdadi in 2012 before splitting away, has decided attempts to start a “moderate” Syrian opposition military movement, in competition with itself, are best strangled at birth.

This sometimes happens even before birth, as was shown last week when al-Nusra abducted Nadeem Hassan, the leader of a small faction trained by the US after careful vetting. And last year, al-Nusra wiped out two groups, the Syrian Revolutionary Front and Harakat Hazm, who were being trained and supplied by the CIA as “a third force” opposed to both Assad and the extreme jihadis.

So far, Isis has not done too badly out of Turkey’s “game-changing” turn against it. Because of disagreement over aid to the Syrian Kurds, American warplanes have not yet started using Incirlik and, if and when they do, Isis will have had more than a week to change the disposition of its forces in preparation for a heavier air assault. If US aircraft based at Incirlik are forbidden to attack Isis fighters when they are battling either the Syrian Kurds or the Syrian army, the militants’ two main opponents on the ground, then they will be no worse off militarily than they were before. This may explain why Isis has responded so little to the US-Turkish agreement that is supposed to deal it a crippling blow. Close observers of the Syrian armed opposition in northern Syria say that it welcomes the Turkish attack on the PKK.

ORDER IT NOW

Were world leaders just a bit simple-minded or ill-informed when they congratulated Turkey on finally turning against Isis? Probably there is as much cynicism as naivety at work here since their intelligence services will have told them that Turkey has long been giving covert support to Isis and al-Nusra, the most important element of which was not closing the border. The main concern of European countries is the actions of their citizens who have joined Isis or al-Nusra and may return home to commit atrocities. Given this preoccupation, governments may calculate that whatever Turkey does or does not do, the Turkish-Syrian border will be more closely guarded in future.

But in terms of the stability of the region President Barack Obama may turn out to have made a poor deal with Turkey. It will not be a killer blow to Isis and may not even weaken it, but it will hit the Kurds who have been IS’s most resolute opponents. It will spread the violence stemming from the civil wars in Iraq and Syria into Turkey. And it will rekindle a Kurdish-Turkish civil war that had long been on the wane.

The game may have changed but peace is even further away.