The British plan was as follows. In order to pinch out the German salient and reach the old Amiens Defence Line, five to seven miles ahead of the existing front, attacks were to made against three successive objectives, the forward German defences, the reserve localities and gun lines, and finally what were believed to be only scattered enemy strongpoints. As at Cambrai, preliminary bombardment was dispensed with, in order to heighten surprise, but a lifting barrage was scheduled t move just ahead of the first wave of tanks. Two-thirds of the British guns were assigned to counter-battery tasks. At the same time the R.F.C.(Royal Flying Corps) would attack German aerodromes to reduce enemy air activity and other aircraft were to give close support to the advancing troops; however, railway junctions were not to be attacked until evening as it was considered that 12 hours would elapse before enemy reserves, set in motion by the attack, would be within striking distance. On the eve of battle the British Fourth Army had a striking force of 13 divisions (plus three available in (G.H.Q. reserve), supported by 1386 field guns and howitzers and 684 heavy pieces, 342 heavy tanks, 72 whippets )light tanks) and 120 supply tanks.
The ground to be crossed, between the Avre and Somme rivers, was a rolling plateau well suited for the employment of tanks. In front of the French, on the extreme right, it was a "real billiard table" but, on the British front, it was scooped by hollow depressions leading towards the rivers. There were a few large villages, usually surrounded by orchards so that they resembled woods, which would also obstruct the advance. On the Canadian right the plateau was cut by the valley of the Luce, which, though a mere stream in August, presented obstacles in the form of swamp, pools and small belts of trees. On the extreme left the plateau was little more than a flat-topped ridge; however, spurs and re-entrants made it unsuitable for tank operations where it sloped towards the rivers.
The Canadian Corps was to attack on a 3 three-division front of approximately 7000 yards, with the 4th Canadian Division in reserve. The most difficult task fell on the 3rd Division on the right; in addition to having to effect a crossing over the Luce in the beginning it had to maintain contact with the French who, unsupported by tanks, were not to move, without a preliminary bombardment. The 3rd Division was to attack its first objective with two brigades; the reserve brigade would than take over for the second objective. The final phase on this front would be undertaken by the 4th Division brought forward from reserve. The 1st and 2nd Canadian Divisions, centre and left, were each to attack with one brigade forward and merely leapfrog a fresh brigade forward for each succeeding phase. The Canadian Independent Force of two motor machine-gun brigades, a cyclist battalion and a section of medium trench mortars was to protect the right flank and maintain liaison with the French. British tank battalions were to lead the assault on each divisional sector and R.F.C. aircraft were detailed to work with the tanks. The Australian Corps on the left was to assault in a similar manner, but with two of its four assaulting divisions advancing abreast on a front of roughly 7500 yards. The battle worn 1st Australian Division was in reserve. On the extreme left the British 3rd Corps was given only the limited task of keeping abreast of the Australians, to be undertaken in two phases.
Although the proposal had been Haig's and the plan evolved mainly by Rawlinson, it was Foch who first proposed an enlargement of the original scheme. At an important conference held on 5th August he directed that, if the initial attack was successful, reserves should be pushed south-eastwards as far as possible. During this stage the Cavalry Corps would be held ready to pass through anywhere there was an opening. It may e noted that the Canadian Cavalry Brigade was serving with the 3rd Cavalry Division, which had been placed under the command of the Canadian Corps until the breakthrough had been accomplished when it, and the cavalry brigade and whippet tanks placed at the disposal of the Australian Corps, were to revert to Calvary Corps command.