Turkey's six-week old invasion of the Syrian Kurdish enclave of Afrin has put it on a collision course with both Russia and the United States.
Ankara has stepped up air strikes on Afrin to provide cover for ground operations, killing 58 Syrian government fighters deployed to reinforce Kurdish units there.
Although Russia could come under pressure from its ally, Syria, to prevent Turkish air raids and halt the advance into Afrin of Turkish troops and militia, it has not, so far, acted. The Kremlin fears that clashes with Turkey could result in it withdrawing co-operation from Russia's and Iran's efforts to impose ceasefires across Syria and halt the seven-year war.
The Pentagon has warned that the Afrin offensive has disrupted the fight against Islamic State remnants in Syria's eastern Deir al-Zor province. Some 20,000 Kurdish fighters from the US-sponsored Syrian Democratic Forces (SDF) have travelled west from SDF-held territory to reinforce Afrin's defenders.
The withdrawal of the Kurds, the SDF’s backbone, has left Arab recruits to guard this large area, comprising 25 per cent of Syria, and repel attacks by Islamic State holdouts. US and SDF forces have suspended offensive operations against the jihadis and are relying on US air strikes to contain them.
US commanders fear they could escape into Jordan or Turkey and, from the latter, infiltrate Europe.
Kurd ‘terrorists’
US-Kurdish clashes with Turkey could erupt if, after securing Afrin, Turkey attacks Manbij, a town captured by the SDF and US special forces in 2016. Manbij is the next stated objective in Turkey's drive to wrest from Syrian Kurds a wide "security zone" along the Syrian side of the border. Ankara brands the Kurds "terrorists" as they are tied to Turkey's insurgent Kurds.
During a recent visit to Ankara, US secretary of state Rex Tillerson appeared to suggest an SDF withdrawal from Manbij, on the eastern side of the Euphrates river, when he indicated the US could fulfil its earlier pledge to secure SDF withdrawal to the river's western bank. This could, however, embolden Turkey to carry on with its offensive against Syria's Kurds in order to cut their land links with Turkey's restive Kurds.
Turkey is also challenging Russia and Syria in the northwestern province of Idlib, designated a "deconfliction" or ceasefire zone, by using Turkey's presence as monitor to take control.
Turkey has forged an alliance, dubbed the Syrian Liberation Front, between non-al-Qaeda fundamentalist factions with the aim of eliminating dominant al-Qaeda affiliate Levant Liberation. The objective of Turkey, which seeks to topple the Syrian regime, is to use Idlib as leverage on Syria and its ally, Russia, to secure concessions in future negotiations.
Neither Syria nor Russia can afford to permit Turkey to attain this goal. Consequently, the Syrian army, backed by Russian air power, has begun operations in Idlib. Once the army has retaken eastern Ghouta, the bulk of its forces are likely to shift to the Idlib front, where they could clash with the Turkish army and allied militia.
Neither Russia nor the US wants to tackle Turkey over its risky military moves as Ankara, thanks to an accident of geography, remains a leading actor in the Syrian and regional theatres.