It was hoped once in Pentagon its “New Syrian Army” and US Special Forces would march out from Jordan east and take the length of Syrian-Iraqi border all the way to Abu Kamal (al-Bukamal) on the banks of Euphrates.
That hope was crushed when the New Syrian Army fell apart, and finally when the real Syrian army bottled up US forces and rebels on their payroll at al-Tanf against the Jordanian border in a shock offensive.
Then it was hoped Abu Kamal would be taken by the Kurdish-dominated and US-augmented SDF coalition from the north. The SDF would race down south, beat the Syrian army to the Iraqi border, turn around and cross the Euphrates to take Abu Kamal — the biggest town in the province after the provincial capital of Deir Ezzor, and the key Syrian-Iraqi border crossing in the Euphrates valley.
For a while it looked like the SDF was on a good way to get there. The Syrian army made a strong start to the final lap of the race for Euphrates by breaking the siege of Deir Ezzor and with Russian help even established an important bridgehead on the left bank of the river, before heading south to the medium-sized town of Mayadin. Then a series of major defections of tribal fighters conscripted by ISIS to the SDF handed the lead to the American-Kurdish coalition.
(Russian spokespeople insisted at the time this was evidence of American/Kurdish collusion with ISIS, but actually the Russian-Syrian side has likewise facilitated tribal defections to its side, with some success, for example in eastern Raqqa.)
Defection deals netted SDF large swathes of territory on the Euphrates’ left bank so that they were now far closer to the Iraqi border and Abu Kamal than the Syrian forces in the valley.
Moreover the territory gained included Syria’s best oil fields. Even if Syria was never a major oil producer like neighboring Iraq, and those fields have been extensively bombed in the war and can’t be made operational again without massive investment it was now 1:0 for the US-backed Kurds.
Until Iraqi army and militias launched an offensive from its side of the border up the right bank of the Euphrates valley. The Iraqis dealt ISIS a huge blow by quickly over-runing the town of al-Qaim which is adjacent to Abu Kamal but lies on the Iraqi side of the border and was the largest town still in ISIS hands with a pre-war population of 150,000.
The fact the southern Syrian flank was now covered by Iraqi army, while ISIS’ own flanks in the desert were dangerously exposed allowed the Syrian army to quickly march on Abu Kamal — not down the Euphrates valley where they would meet stiff resistance in every built-up area along the way, but across the open desert to the west.
During the fighting for Qaim Iraqi forces moved a few kilometers into Syria to better maneuver against the enemy, and at least one Iraqi militia commander declared publicly his forces would join the fight for Abu Kamal as well.
Moreover, thousands of Iraqi Shia volunteers have fought on the Syrian loyalist side for years now, so there is little doubt Iraqis are taking part in the fighting in Abu Kamal on the pro-government side, the question is merely how big their presence is.
Nonetheless, the major Iraqi contribution to the battle was in that for once the Syrians could advance eastward along the border with their flank facing the Iraqi Anbar province covered – with ISIS’ flank exposed for a change.
As of now the fighting for the Syrian border town is still ongoing, but there is no doubt it will be the Syrian army that establishes its control over it, rather than the Pentagon-augmented SDF.
With oil on the left bank in Kurdish hands, and the key town on the right bank in government hands the race for Euphrates looks to finish with the score of 1:1. Whether the predominantly Kurdish force can hold onto the oil so far from Kurdish-populated areas of Syria for the long term remains to be seen however.