The limited participation of Prince Feisal's force had been invited on 21 September, when an RAF aircraft delivered news of Allenby's successful offensive and the destruction of the Ottoman Seventh and Eighth Armies, to its forward base at Azrak.
The aircraft also carried instructions from Lieutenant Colonel Alan Dawnay, responsible for liaison between the EEF and the Arabs, informing Prince Feisal that they had closed all escape routes, except the Yarmuk Valley, which lay east of the Jordan.
The message exhorted the Arabs to attempt to cut off this route and it was made clear to Prince Feisal that his force was not to "embark on any enterprise to the north, such as an advance on Damascus, without first obtaining the consent of the commander-in-chief."

Allenby wrote to Prince Feisal:
There is no objection to Your Highness entering Damascus as soon as you consider that you can do so with safety.
I am sending troops to Damascus and I hope that they will arrive there in four or five days from to-day.
I trust that Your Highness' forces will be able to co-operate, but you should not relax your pressure in the Deraa district, as it is of vital importance to cut off the Turkish forces which are retreating North from Ma'an, Amman and Es Salt.

— Allenby letter to Prince Feisal 25 September 1918
As the remnants of the Ottoman Fourth Army retreated northward via Deraa they were pursued over "many waterless miles", by Arab forces which "joined Feisal's force, with horrific consequences."
Three quarters of Prince Feisal's 4,000-strong force including Nuri esh Shalaan's camel force, were irregulars.
They had made a forced march overnight on 26/27 September, crossing the railway north of Deraa and tearing up rails to arrive at Sheikh Sa'd 15 miles (24 km) north northwest of Deraa, at dawn on 27 September.
Auda abu Tayi captured a train and 200 prisoners at Ghazale Station, while Talal took Izra' a few miles to the north.
A total of 2,000 prisoners were captured between noon on 26 September and noon on 27 September, when the Anazeh, an Arab tribal confederation attacked the rearguard defending Deraa.
Fighting in the town continued into the night.

At Deraa Lieutenant Colonel T. E. Lawrence and Colonel Nuri Bey met Barrow when the 4th Cavalry Division entered the town on 28 September, agreeing to cover the division's right flank during their pursuit north to Damascus.
The limited participation of Prince Feisal's force had been invited on 21 September, when an RAF aircraft delivered news of Allenby's successful offensive and the destruction of the Ottoman Seventh and Eighth Armies, to its forward base at Azrak. The aircraft also carried instructions from Lieutenant Colonel Alan Dawnay, responsible for liaison between the EEF and the Arabs, informing Prince Feisal that they had closed all escape routes, except the Yarmuk Valley, which lay east of the Jordan. The message exhorted the Arabs to attempt to cut off this route and it was made clear to Prince Feisal that his force was not to "embark on any enterprise to the north, such as an advance on Damascus, without first obtaining the consent of the commander-in-chief."
Allenby wrote to Prince Feisal:
There is no objection to Your Highness entering Damascus as soon as you consider that you can do so with safety. I am sending troops to Damascus and I hope that they will arrive there in four or five days from to-day. I trust that Your Highness' forces will be able to co-operate, but you should not relax your pressure in the Deraa district, as it is of vital importance to cut off the Turkish forces which are retreating North from Ma'an, Amman and Es Salt.
— Allenby letter to Prince Feisal 25 September 1918
As the remnants of the Ottoman Fourth Army retreated northward via Deraa they were pursued over "many waterless miles", by Arab forces which "joined Feisal's force, with horrific consequences." Three quarters of Prince Feisal's 4,000-strong force including Nuri esh Shalaan's camel force, were irregulars. They had made a forced march overnight on 26/27 September, crossing the railway north of Deraa and tearing up rails to arrive at Sheikh Sa'd 15 miles (24 km) north northwest of Deraa, at dawn on 27 September. Auda abu Tayi captured a train and 200 prisoners at Ghazale Station, while Talal took Izra' a few miles to the north. A total of 2,000 prisoners were captured between noon on 26 September and noon on 27 September, when the Anazeh, an Arab tribal confederation attacked the rearguard defending Deraa. Fighting in the town continued into the night.
At Deraa Lieutenant Colonel T. E. Lawrence and Colonel Nuri Bey met Barrow when the 4th Cavalry Division entered the town on 28 September, agreeing to cover the division's right flank during their pursuit north to Damascus.
Capture of Damascus