However, the Arab Movement lived on Allenby’s good pleasure, so it was needful to undertake some operation, less than a general revolt, in the enemy rear: an operation which could be achieved by a raiding party without involving the settled peoples; and yet one which would please him by being of material help to the British pursuit of the enemy. These conditions and qualifications pointed, upon consideration, to an attempted cutting of one of the great bridges in the Yarmuk Valley.
It was by the narrow and precipitous gorge of the River Yarmuk that the railway from Palestine climbed to Hauran, on its way to Damascus. The depth of the Jordan depression, and the abruptness of the eastern plateau-face made this section of the line most difficult to build. The engineers had to lay it in the very course of the winding river valley: and to gain its development the line had to cross and recross the stream continually by a series of bridges, the farthest west and the farthest east of which were hardest to replace.