Turkey gearing up to destroy Al-Qaeda's offshoot in Syria
The following day, Turkey fired artillery at the HTS across the border in support of the FSA. However on the very same day a Turkish Army "reconnaissance team" entered Idlib and were reportedly escorted by HTS fighters, leading to speculation that Ankara may yet try to make some kind of a last-minute deal with the group.
Such a deal, aiming to avert a confrontation, may well also be in the interests of HTS, which is working earnestly to retain and consolidate its control over that corner of Syria.
HTS hasn't yet attacked Turkey, perhaps to avoid any serious retaliation which could uproot them.
Furthermore, the Turkish government is clearly more interested in fighting the Syrian Kurdish People's Protection Units (YPG) in the same region.
After the four de-escalation zones in Syria were agreed between Russia, Turkey and Iran earlier this year, the Russians and the Turks were talking about a joint deployment of forces over the summer - which failed to materialise. As with the Islamic State group, HTS were never included in ceasefire deals in Syria given their extremely violent nature.
In June, the HTS warned that any Turkish troop presence in Idlib would be viewed by them as an aggressive "foreign intervention" and treated as such.
Then in July, Ahrar al-Sham, an Islamist group backed by Turkey, was defeated by HTS - substantially reducing Ankara's options in the province. Turkey invariably relies on proxy ground forces to defeat its enemies in Syria, as it did using Free Syrian Army (FSA) militiamen during the seven-month Euphrates Shield operation against IS.
|Watch: Airstrikes in Idlib
Ankara is now using the same FSA fighters in Idlib. The Turks say they have learned from the shortcomings these fighters exhibited during Euphrates Shield and have since given them more adequate training and weaponry. It is yet to be seen if this will make them a more effective fighting force as they enter battle against the ruthless militants of HTS.
Only the FSA, Erdogan says, is in Idlib fighting on the ground. Russia is providing air support and the Turkish military is supporting the operation "from inside Turkey's borders".
A Russian airstrike already reportedly wounded, and put into a coma, Abu Muhammad al-Golani, the founder of the Nusra Front - one of HTS' parent groups - and killed 12 of the group's field commanders.
More tanks and vehicles from the Turkish army have arrived at the Turkey-Idlib border. It's unclear if Turkish special forces infantry and armour will enter Idlib behind the FSA. Turkey will likely rely heavily on cross-border artillery strikes using its T-155 Firtinia self-propelled artillery guns - which can hit targets from 40 kilometres away - to support any FSA push until it gets deeper into Idlib.
Then it may well send in its own supporting forces on the ground behind the FSA offensive.
Read more: Turkey's interests in Syria don't include the people of Idlib
During the final battle of Euphrates Shield against IS in the city of Al-Bab, Turkey had to reinforce FSA fighters, who endured heavy casualties, to the extent that the number of regular Turkish troops fighting on the ground equalled the number of FSA fighters.
According to a group within this FSA proxy force the Russians are only operating on the periphery of Idlib from Syrian regime-controlled territories, and will not enter the province.
Russian air power already supported Euphrates Shield during the Al-Bab battle earlier this year, meaning direct Russian military backing of a Turkish-backed offensive in Syria will not be without precedent. Moscow controls the airspace above northwest Syria and Russian assent is essential for Turkey if it wants to provide air support to the FSA.
There was a week during Euphrates Shield last November when Turkish jet fighters did not enter Syrian airspace after the regime threatened to shoot them down. Only by going to the Russians was Turkey able to continue carrying out airstrikes. Supporting air power will likely prove essential for Turkish success against HTS in Idlib.
As the Turkish military expert Metin Gurcan recently pointed out, during the Al-Bab battle "the lack of close air support by warplanes and attack helicopters and force protection by attack helicopters for temporary military outposts, as well as the inability to fly missions to evacuate wounded troops and provide logistical support, bore markedly on the campaign".
These lessons undoubtedly need to be applied in the coming weeks and months to any major campaign in Idlib.
|The three provinces of Jazira, Kobane and Afrin are under defacto Kurdish control, much to the ire of Ankara
The Turkish army, in the words of one Al Monitor columnist, has made itself at home in the northwestern swathes of Syrian territory it captured from IS in Euphrates Shield. Aside from removing IS from the border the clear aim of that operation was to stop Kurdish YPG forces from linking up their northeastern Syrian territories with the isolated Kurdish Afrin canton bordering Idlib. Any Turkish move into Idlib will enable them to completely surround Afrin, which they've already encircled on their own territory to the north and west and from the east on Syrian territory controlled by the FSA. Idlib is situated south of Afrin.
Russia is unlikely to permit a simultaneous Turkish assault on Afrin. They have deployed military police to the Kurdish enclave to de-escalate clashes between the YPG there and Turkey's FSA proxy. Ankara threatened to invade Afrin over the summer but settled for bombarding it several times with cross-border artillery strikes.
Now, if it succeeds in forcing HTS from Idlib and maintaining a presence there, either directly or through its proxy, they will have Afrin completely boxed in, cut off further from the rest of the Kurdish territories in Syria and even more vulnerable to any future Turkish attacks.
Paul Iddon is a freelance journalist based in Erbil, Iraqi Kurdistan, who writes about Middle East affairs.
Follow him on Twitter: @pauliddon