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Two squadrons were reserved for close air support on the battlefield and low attacks on German airfields. The British planned to advance on a 17,000-yard (16,000 m) front, from St. Yves to Mt. Sorrel east to the Oosttaverne line, a maximum depth of 3,000 yards (2,700 m). Three intermediate objectives to be reached a day at a time became halts, where fresh infantry would leap-frog through to gain the ridge in one day. In the afternoon a further advance down the ridge was to be made. The attack was to be conducted by three corps of the Second Army (General Sir Herbert Plumer): II Anzac Corps in the south-east was to advance 800 yards (730 m), IX Corps in the centre was to attack on a 5,000 yards (4,600 m) front, which would taper to 2,000 yards (1,800 m) at the summit and X Corps in the north had an attack front of 1,200 yards (1,100 m). The corps planned their attacks under the supervision of the army commander, using as guides, the analyses of the Somme operations of 1916 and successful features of the attack at Arras on 9 April. Great care was taken in the planning of counter-battery fire, the artillery barrage time-table and machine-gun barrages.
German artillery positions and the second (Höhen) line were not visible to British ground observers. For observation over the rear slopes of the ridge, 300 aircraft were concentrated in II Brigade RFC and eight balloons of II Kite Balloon Wing were placed 3,000–5,000 feet (910–1,520 m) behind the British front line. The Second Army artillery commander, Major-General George Franks, co-ordinated the corps artillery plans, particularly the heavy artillery arrangements to suppress German artillery, which were devised by the corps and divisional artillery commanders.
