page_title: Western Front tactics, 1917
section_title: Corps
hierarchical_section_title: Western Front tactics, 1917 / Operational surprise, Cambrai, 1917 / Corps
caption_attribution_description: A British Mark IV tank at Wailly. This shows how it would appear to occupants of the German trenches during the Battle of Cambrai. This was the first occasion on which tanks were launched en masse in a surprise attack and it clearly demonstrated the potential of the armoured vehicle - 21 October 1917
context_page_description: In 1917, during World War I, the armies on the Western Front continued to change their fighting methods, due to the consequences of increased firepower, more automatic weapons, decentralisation of authority and the integration of specialised branches, equipment and techniques into the traditional structures of infantry, artillery and cavalry. Tanks, railways, aircraft, lorries, chemicals, concrete and steel, photography, wireless and advances in medical science increased in importance in all of the armies, as did the influence of the material constraints of geography, climate, demography and economics. The armies encountered growing manpower shortages, caused by the need to replace the losses of 1916 and by the competing demands for labour by civilian industry and agriculture. Dwindling manpower was particularly marked in the French and German armies, which made considerable changes in their methods during the year, simultaneously to pursue military-strategic objectives and limit casualties.
context_section_description: Corps planning for the Cambrai operation followed the routine established in early 1917. IV Corps (Lieutenant-General Sir C. L. Woolcombe) issued its draft plan on 31 October, giving the concept of the plan, the three stages and the troops allotted, with the measures needed to prepare the area and plan the assembly of troops. Administrative, intelligence and signalling instructions, were issued by the respective corps staff branches. During planning, IV Corps issued more instructions regarding the role of its divisions, particularly for the period after the Hindenburg Support Trench system was captured, laid down that the Tank Corps was to use all its tanks on the first day and that the troops involved in the attack, would move to the front immediately before the attack, rather than a few days previous, to be fresh and to prevent the Germans making deductions from prisoners. This decision gave the infantry more time for training with the tanks and responsibility for this was delegated to infantry division commanders and the tank brigade attached to IV Corps. Further instructions were issued from 10–17 November on concentration and assembly, secrecy, preliminary movements, communication of orders, codes and ciphers, signals, later stages of the attack and cavalry liaison.
  The Tank Corps also followed this routine, by sending recommendations about the distribution of its units, the training of tanks and affiliated infantry for approval by the Third Army HQ. The proposals were based on the "Notes" issued on 4 October, which summarised the experience gained by the Tank Corps since April and amendments were issued on 10 November. The Third Army HQ issued two "Notes" on 30 October, covering tank-infantry training and operations. In "Tank and Infantry Operations Without Methodical Artillery Preparation" of 30 October, each corps was told to keep the instructions secret to ensure surprise, that tank sections should attack specific areas, objectives should be reserved for an echelon of tanks each, that an advanced tank should keep German heads down, while the main body and infantry crossed German trenches, that the main body of tanks should stay on the British side of the German line being attacked, that tanks would be allotted according to the number of German positions in the area and work in threes to cover 100–200 yd (91–183 m) of front. Only a platoon of infantry should work with each tank, to avoid bunching when moving through lanes in barbed wire made by the tanks and that infantry should move in section files. Further sections described the care needed when tanks crossed barbed wire, so that following tanks would not pull up the wire, the use and marking of trenches filled by fascines and the principles of tank-infantry co-operation.
  In "Notes on Infantry and Tank Operations" 30 October, Third Army HQ described the characteristics of the tanks and the Tank Corps organisation, how to identify individual tanks, the frontage per tank, formations, assembly, concealment, the method of moving forward to the attack, tank objectives, infantry co-operation, portage of ammunition, wire and trench crossing, signalling, counter-battery work, staff liaison and reporting and stated that success depended on the mechanical fitness of the tanks, efficient assembly on the battlefield, the selection of obvious objectives, the use of prepared and concealed approaches and thorough briefing of all tank and infantry officers. Third Army HQ delegated operational control of the tanks to III and IV Corps, which allocated tanks to their divisions for division commanders to arrange training. Each corps sent a staff liaison officer to the tank brigade headquarters attached.
  The RFC continued its development of ground attack operations, with a more systematic organisation of duties and coverage of the battlefield, drawing on the lessons of the Third Battle of Ypres and the pioneering work done during the capture of Hill 70 in August. The smaller area of operations at Cambrai and the growth of the RFC meant that more aircraft could be allotted to each 
caption: British Mark IV tank at Wailly
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