to Arras, rather than southwards to Péronne. An increase in the number of trains moving from Germany to Belgium was discovered but the quality of German troops opposite the British was thought to have been much reduced. The true number of German divisions in reserve in France was ten, with six opposite the British, double the number the British knew about. Reports of work continuing on the German defences opposite the Fourth Army in March and April, led the planners to adopt a less optimistic view, particularly due to the news about very deep shell-proof shelters being dug under German front trenches, which were far less vulnerable to bombardment. Plan British planning for the offensive had begun in April, with a Fourth Army proposal for a methodical advance to the high ground around Thiepval and thence to the Bapaume–Péronne road. Haig had exhaustive negotiations with Joffre and rejected the concept in favour of the capture of the ridge north of Péronne to assist a French crossing of the Somme further south. Diversion of French divisions to Verdun and the assumption by the British of the main role in the offensive, led to revisions of the plan towards an ambitious attempt at strategic attrition, through a breakthrough and a battle of manoeuvre with distant objectives. The French Sixth Army, in GAN, was the last of the three French armies originally intended for the Somme, the Tenth Army and Second Army having been sent to Verdun. Joffre placed XX Corps north of the river, next to the British XIII Corps, the southernmost Fourth Army formation. British plans were made by a process of negotiation between Haig and General Henry Rawlinson, the Fourth Army commander. Haig became more optimistic at what could be achieved early in an offensive, given the examples of Gorlice-Tarnów in 1915 and at Verdun early in 1916. Rawlinson favoured a methodical attack from the beginning of the offensive, in which belts of the German defences about deep, would be pulverised by artillery and then occupied by infantry. An attempt to reach deeper objectives towards the German second position, risked infantry being counter-attacked beyond the cover of field artillery but had the advantage of exploiting a period when German artillery was being withdrawn. On 16 April, Rawlinson announced the objectives to the corps commanders, in which III, X and VIII corps would capture Pozières, Grandcourt and Serre on the first