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The memorandum issued by GHQ on 14 December 1917 outlined defensive principles heavily based on captured German documents (L.E. Kiggell, ‘GHQ Memorandum on Defensive Measures’, 14 December 1917, National Archives CAB 24/38 Image No 0011.). British attempts to emulate this system resulted in fundamental differences in both interpretation and application. In the Outpost Zone, called the Forward Zone by the British, the BEF approach differed from the Germans in three key respects; location, manning, and withdrawal authority. The BEF like the Germans defended their Forward Zone from a succession of trench lines and strongpoints but, unlike the Germans, these defences were based around the original front line trench systems so minimal consideration could be given to the essential elements of terrain and observation. Manning levels also differed; on average BEF divisions occupying the Front allocated approximately 30% of their infantry strength, 3 battalions, to defend the Forward Zone as compared to the Germans who would allocate only 15%.
Inconsistencies between neighbouring BEF units resulted in over 50% of the manpower being allocated to the Forward Zone by some divisions. On 3rd Armies southern boundary 140th Brigade [47th (2nd London) Division, V Corps], holding the line alongside 26th Brigade [9th (Scottish) Division, VII Corps, 5th Army], had be directed ‘to fight for and hold the front line at all costs’. 26th Brigade had been instructed ‘to fight for the battle zone not for the forward zone’ (Travers, How the War was Won, p. 57.). Inconsistencies were not just evident between armies. In 5th Army there were differences between corps and even between divisions within the same corps. XVIII Corps were ordered to hold the line in depth whereas the neighbouring III Corps were to hold the front in strength (Travers, How the War was Won, p. 64.). In fairness to III Corps part of the reasoning for them having to strengthen the Forward Zone was linked to the fact that their Battle Zone had not been completed, being the last section of the line to be taken over from the French. In VII Corps Congreve, the corps commander, believing that 16th (Irish) Division was vulnerable to a surprise attack over ruled the division commander and pushed 5 of the division’s battalions into the Forward Zone (Middlebrook, The Kaisers Battle, p 200.).
These inconsistencies can to a degree be attributed to the variable status of the BEF Battle Zone. GHQ had provided clear direction on this:
‘Until the battle zone has been strengthened there can be no alteration in existing, methods of defence.’. Kiggell, ‘GHQ Memorandum on Defensive Measures’, p. 3.
Arguably the difference that was to have most effect was that of withdrawal authority. Unlike the German system local commanders in the BEF could not make the decision to withdraw. Orders from GHQ stated:
‘The troops allocated to the defence of the outpost zone [forward zone] will do all in their power to maintain their ground against every attack. Garrisons of works and localities will hold their defences at all cost, and local reserves will counter-attack immediately, without waiting for orders, should the enemy succeed in penetrating the defences.’. Kiggell, ‘GHQ Memorandum on Defensive Measures’, p. 3.
These differences in interpretation and application led the BEF to treat the Forward Zone as little more than a heavily defended trench line with little tactical flexibility. During Operation Michael this was to prove catastrophic.
Confusion over the function of the Battle Zone also existed. The emphasis on holding ground also pervaded here compromising the key element of the defence-in-depth system, the counter attack:
'The battle zone has been designed to include all ground which for various reasons should be held at all costs, and with a view to the main resistance being made, as far as possible, on ground favourable to us.'. Kiggell, ‘GHQ Memorandum 3 January 1918’, National Archives CAB/24/38 Image No 0011, pp. 5-6.
'The battle zone, being the ground on which it has been decided to give battle should the enemy attack in strength must be maintained.'. Kiggell, ‘GHQ Memorandum on Defensive Measures’, p. 3.
Each front line BEF division had at least 3 battalions available to man the Battle Zone, with a fourth in reserve for local counter attacks (Randal Gray, Kaiserschlacht 1918 The Final German Offensive (London: Osprey,1991), p 33.). This allocation of 25% of the infantry strength as counter attack forces in the Battle Zone was significantly less than the German 80%. The German system also stipulated that reserve divisions located in the Rear Zone were kept close enough to beat an attacker to the Battle Zone. What BEF reserves there were, during the Michael offensive, were kept at least 10 miles behind the Battle Zone arriving too late to fulfil a counter attack role. The key elements of the German system; flexibility and the counter attack were compromised by the BEF's fixation on holding ground:
' ... the Germans viewed a defensive system primarily in terms of the men and weapons deployed in the zone, allowing reorganization to be rapid and easy, the British appear to have thought of the defensive system more in terms of the physical defended positions, such as earthworks and wire. To reorganize such a system required enormous amounts of labour and was a slow process.'. Martin Samuels, Doctrine and Dogma: German and British, Infantry Tactics in the First World War (New York:Greenwood Press, 1992), p 54.
Travers' assessment that the BEF, particularly in the area attacked on 21 March 1918, had failed to emulate the German defence-in-depth system was correct. What is open to debate however is whether the defensive system, even correctly applied, could have withstood the scale of the German assault on 21 March 1918.
Next: Operation Michael