Remarkable, seven months ago the army was stil battling for eastern Aleppo, thought of relieving Deir ez-Zor was a distant dream
Since the last update the Syrian army has entered Dalhah village on the Euphrates, which means the US-augmented Kurdish-dominated SDF militia on the river's right bank has now been completely penned in.
On the other hand, there are reports of substantial communication between the Russians, the Syrian army, and the Kurds — which raises the possibility that the cut off was achieved in a cordial manner with the prior acquiescence of the SDF and possibly even the US.
The SDF certainly has its hands full with the battle for Raqqa city, and there's Ankara saber rattling in the north as well. Investing more into the race for Euphrates would easily overstretch its resources.
Meanwhile, the Syrian army also finally broke ISIS lines in front of Suknah and and has begun the battle for the town itself. Suknah is the strategic midpoint between Palmyra and Deir ez-Zoir. Taking the town opens up the possibility of relieving the encircled Deir ez-Zoir from the west.
To really appreciate the obstacle that is Suknah and the significance of overcoming it you have to take a look at the relief map of its surroundings. The road from Palmyra eastwards to Suknah goes through rugged terrain and is dominated by highlands to its north. However after Suknah the terrain quickly opens up. Thus after the slog that fighting from Palmyra to Suknah has been the Syrian advance over open desert may greatly accelerate.
Right now, however, the relief for the besieged city looks likeliest from the north. A mix of Syrian army regulars, led by the elite Tiger Forces, and local pro-government tribal fighters has just entered northern Deir ez-Zoir province—restoring a Syrian government presence that had been absent for years—and is now just some 60 kilometers from the city.
Tigers are advancing across open desert just outside the populated belt around the Euphrates, which is faster than going through the built-up valley. This leaves their flank exposed, but on the other hand it also threatens ISIS with encirclement.
Just slightly over half a year ago the Syrian army was still fighting for eastern Aleppo, and had just lost Palmyra to an ISIS counter attack. Now it is well on its way to relieve the siege of Deir ez-Zoir and make a return to the middle Euphrates valley. Truly remarkable.