tactics and a strong record of success over the past two years. The tactical methods had been tested by the Australians in a local counter-attack at the Battle of Hamel on 4 July. The German defenders of Hamel were deeply dug in, and their position commanded a very wide field of fire. Similar positions had resisted capture for two months in the Battle of the Somme. The Australians had used surprise rather than weight at Hamel. The artillery had opened fire only at the moment the infantry and tanks advanced, and the Germans were rapidly overrun. A key factor in the final plan was secrecy. There was to be no artillery bombardment a significant time before the attack, as was the usual practice, only fire immediately prior to the advance of Australian, Canadian, and British forces. The final plan for the Fourth Army involved 1,386 field guns and howitzers and 684 heavy guns, making up 27 medium artillery brigades and thirteen heavy batteries, in addition to the infantry divisions' artillery. The fire plan for the Fourth Army's artillery was devised by Monash's senior artillery officer, Major General C. E. D. Budworth. British sound ranging advances in artillery techniques and aerial photographic reconnaissance made it possible to dispense with "ranging shots" to ensure accurate fire. Budworth had produced a timetable which allowed 504 out of 530 German guns to be hit at "zero hour", while a creeping barrage preceded the infantry. This method was similar to the Feuerwalze which the Germans themselves had used in their Spring Offensive, but its effectiveness was increased by the surprise achieved. There were also to be 580 tanks. The Canadian and Australian Corps were each allocated a brigade of four battalions, with 108 Mark V fighting tanks, 36 Mark V "Star", and 24 unarmed tanks intended to carry supplies and ammunition forward. A single battalion of Mark V tanks was allocated to III Corps. The Cavalry Corps were allocated two battalions each of 48 Medium Mark A Whippet tanks. The Allies had successfully moved the Canadian Corps of four infantry divisions to Amiens without them being detected by the Germans. This was a noteworthy achievement and reflected well on the increasingly efficient staff work of the British armies. A detachment from the Corps of two infantry battalions, a wireless unit and a casualty clearing station had been sent to the front near Ypres to bluff