The defeat of Islamic State's territorial caliphate in Iraq and Syria has plunged Syria into fresh conflicts involving local and external forces formerly focused on fighting jihadis.
In the first major post-Islamic State clash pitting the US against Russian and Iranian-backed fighters, US warplanes and gunners repelled an attack by pro-government forces on the headquarters Kurdish forces based in eastern Deir al-Zor province.
This was also the most serious confrontation between the US and Russia since Moscow intervened in the conflict in 2015.
The US deploys scores of war planes and 2,000 special operations troops to train and advise the Kurdish-dominated Syrian Democratic Forces (SDF) militia, numbering 50,000.
Following the successful campaign to drive Islamic State, also known as Isis, from its de facto capital, Raqqa, in north-central Syria, the SDF swept across Raqqa and Deir al-Zor provinces, capturing 25 per cent of Syria and providing the US with a military base to give it political leverage in shaping Syria's future.
Turkey is not prepared to accept this fait accompli. Alienated by the US's sponsorship of the Kurds, this Nato member has now allied with Russia and Iran.
In the northwest of Syria, Turkish troops and tanks, and Syrian Free Army surrogates, have challenged the US by mounting a slow motion offensive against SDF units protecting the Kurdish-majority enclave of Afrin.
SDF reinforcements have arrived from the town of Manbij, another US base, depleting defenders and causing concern among US commanders.
Turkish warning
Turkish president
Recep Tayyip Erdogan
has repeatedly warned Washington to withdraw its troops from Manbij, which he intends to attack in a campaign to drive the SDF from the 822km Turkish-Syrian border. He argues the Kurdish SDF component is an offshoot of Turkey’s separatist Kurds, who have been fighting
Ankara
since 1984.
Erdogan and Russian president Vladimir Putin have pledged to co-ordinate military activities and intend to meet in Istanbul to discuss strategy with Iranian president Hassan Rouhani. Russia and Iran back the Damascus regime's objective of recapturing all of Syrian territory and stabilising the country with President Bashar al-Assad remaining in power. Anti-Assad Turkey may have to go along for now with this scenario to maintain the alliance.
US Syria expert Joshua Landis told the France24 satellite channel that Washington seeks to use US Kurdish-held territory to deprive Damascus of oil and agricultural resources. The US will also block reconstruction funds for Syrian territory held by the government – currently 65 per cent of the country – in order to keep Syria "weak", he says, thereby weakening Syria's allies Russia and Iran.
This would suit Israel which, reportedly, intends to use Islamic State, al-Qaeda and other proxies to establish a 40km deep buffer zone to exclude Syrian and pro- Iranian forces from the Golan Heights ceasefire line.
Meanwhile, the Syrian army, backed by Russia and Iran, has continued its mission to regain lost land. Damascus has pounded Saudi-backed jihadis in the Eastern Ghouta, adjacent to Damascus, and al-Qaeda affiliates in northwest Idlib province.
The UN has appealed for a halt to hostilities as civilians remain in both areas, which have been declared “de-confliction” or ceasefire zones by Russia, Iran and Turkey, a move rejected by jihadis.