The Allied plans for 1917 saw separate but coordinated attacks. The British would attack at Arras (and also storm Vimy Ridge) to pin down German reserves and set up Nivelle’s French attack.3 The BEF would be using new methods based on the experience of 1916. Over the winter the BEF had revised its doctrinal manuals; artillery priorities were now 1. counter-battery 2. hitting the German infantry and 3. hammering the German defences. This roughly reversed the 1916 priorities and put more emphasis on the success of the initial attack rather than on a possible deeper penetration.
Counter-battery techniques had made major progress in 1916. In 1915 there had been optimistic hopes of ‘silencing’ all German batteries but the immediate problems caused by machine guns and barbed wire had pushed the counter-battery issues to the bottom of the list. In 1916 there were enough British bombardment resources that counter-battery could be tackled. In general the British began differentiating between neutralising fire (when there was an attack under way) and destructive fire (when the infantry were not in the open), and realised that howitzers were key for destruction and that guns were useful for neutralisation. New technologies also played a role, with flash-spotting (finding German batteries by triangulating their muzzle flashes) and sound-ranging (using newly invented microphones to listen for the sound of a gun firing) used to pinpoint targets, with accuracy as precise as 25 yards. The British proved superior in these fields by pragmatically adopting the latest scientific methods. The technical lead in artillery tactics that emerged during 1917 was hugely facilitated by the proper use of advanced survey techniques. This was in marked contrast to the Germans, who had skilled individuals but often diluted their effectiveness by creating arcane or inefficient systems for solving simple problems – such as not standardising their grid projection so that their gunners often had to consult and cross-reference several maps. Another innovation was organisational: the Counter-Battery Staff Officer would not only have the full range of intelligence sources, he controlled the counter-battery artillery. Of course, the system was only as good as the men – one even resorted to using a ouija board – but it was better than in 1916.
The creeping barrage was also improved. It had proven invaluable in 1916, but the difficult months of experience on the Somme had indicated a number of ways it could be bettered: more depth (several lines of 18-pounder shells), different munitions (high explosive, shrapnel and – new for 1917 – smoke), and more guns (with 4. 5-inch howitzers added ahead of the 18-pounders). This process of improvement would continue throughout 1917. Over the winter of 1916/17 the BEF reorganised its divisional artillery; instead of four pure (either all-gun or all-howitzer) field artillery brigades, divisions were now allocated two mixed brigades, each with three 18-pounder batteries and one 4. 5-inch howitzer battery. This matched the tactics of the barrage: two 18-pounder batteries firing side-by-side, with the third also firing but available to switch to targets of opportunity, while the howitzers were firing on point targets ahead of the 18-pounders. This was also enough guns for a division just holding the line, while the remaining batteries were reorganised into independent Army Field Artillery (AFA) brigades that could be sent wherever they were needed. New technology also affected the field artillery: the new ‘fuse no. 106’ was more sensitive than previous models, detonating efficiently enough on impact to allow howitzers to slice through the tangled mass of barbed wire that earlier shells had merely rearranged. The howitzers’ trajectory also meant that wire could be cut on reverse slopes and experience showed that the howitzers were more efficient, cutting circles in the wire instead of the cones that field guns made; the tactical possibilities were duly noticed and the BEF hoarded the available ‘no. 106’ fuses for the first attack.
Meanwhile, the Germans were not idle in improving their own tactical systems. The new army doctrine, outlined in The Principles of Command in the Defensive Battle in Position Warfare in March 1917, sought to reduce losses by holding deeper zones with fewer forward troops (within range of enemy artillery), dispersing into more but smaller targets, and having better infantry–artillery coordination to both deal with enemy assaults and facilitate counter-attacks. The first zone consisted of outposts, strong enough to defeat small attacks and force a major effort, thus delaying large attacks so the Germans could move up reserves. The main battle zone had more defences and defenders, and its distance from enemy field artillery reduced the effectiveness of bombardments; it could be held against almost any attack. The rear battle zone was out of range of enemy heavy artillery (thus requiring sustained attacks to breach the German defences, and buying time for a German response) and would protect German counter-attack reserves. Artillery and minenwerfers were echeloned in camouflaged positions but the Germans were increasingly aware of the Allies’ superior detection systems, and mobility was seen as the key to survival in the evolving battle: ‘in battle or for special missions, the use of unprepared emplacements will often be advisable’.
For the artillery, the Germans tried to better coordinate with the infantry, including permanently attaching liaison officers to infantry regiments. Artillery command was altered a bit, with divisions getting an Artillerie Kommandeur, a general or senior colonel, who often stayed in a sector when the infantry were relieved to retain familiarity with the ground and conditions. In a quiet sector the Kommandeur would have around 18 batteries, one-third of them heavies (compared with 12 batteries in 1914, none of them heavy), while in an active sector he might have 30 batteries – probably too many for him and his small staff to readily control. A minen-werfer company (18 tubes of mixed calibres) was also intended for each infantry division. Conversely, counter-battery fire was handled by groups run from army level, mainly comprising 150mm and 210mm howitzers. Infantry tactics switched to defence-in-depth, and they sought to fight only for tactically important ground rather than trying to hold everything. The depth also created more defensive positions, and the Germans switched (mostly) from strong positions to many positions; they judged that since the Allied artillery would sooner or later demolish any position the gunners found, it made more sense to have lots of alternatives. Guns should either be protected against 9. 2-inch shells or simply concealed; anything in-between was a waste. Long-range guns were emphasised, and new designs of guns (and shells) were arriving that provided more range. More and more shells were needed, but the Germans had to avoid firing too fast and over-heating the barrels, since this led to premature bursts. This, combined with limitations on production and battlefield transportation, led the Germans to end prolonged intense barrages, until they ended up with only 3 minutes’ intense and 5 minutes’ deliberate fire, unless signals indicated there was a serious attack in progress: observed fire ‘executed calmly and well adjusted by observers, and methodical fires for annihilation, supports the infantry better than automatic barrages which use up an enormous amount of ammunition for a minimum result’. Observed fire was strongly encouraged since it was both more effective and needed fewer shells. By mid-1917 rigid unobserved barrages were deprecated and counter-preparation (essentially an attack-strength barrage fired in the defence) was recommended. This would not stop an attack, but would disorganise it and give the infantry a better chance.
An elastic defence would also allow attackers to penetrate but then bring counter-attacks to catch them when they were weakened, tired, dis-organised and out of communication. Ludendorff described the new layered system as more effective ‘because it forces the enemy in taking it to engage considerable forces and means, which he will lack when he comes to the principal attack. As his advance proceeds, he will encounter difficulties that constantly increase in number and which constantly become un-expected.’ Observation was the key to defence, both for controlling the artillery and for gathering information for effective counter-attacks; ensuring that the key positions were held also denied the Allies good observation posts. Observation was so important that ‘the requirements of the artillery play a decisive part in the selection and preparation of positions’ – in other words the infantry defended where the Allied artillery was minimised and fought to maximise the power of the German artillery. The Germans established a Division Commander School to test and explain all this but it was a new idea and was not easily implemented. The Germans around Arras kept too much strength forward and had their batteries too clumped together. (The British actually hit the isolated batteries first, then the clumps, which were easier to neutralise if destruction failed.)
At Arras the British used their new methods and had more guns. There were enough heavies to subordinate a bombardment group to each attacking division, ensuring better coordination. The Germans called the week-long intense bombardment (counter-battery fire and some trench bombardment had started two weeks earlier) the Leidenswoche (the week of suffering). On Vimy Ridge they knew the British were massing guns and also knew (from a map found on a downed pilot) that their own gun positions were well known to the British, but they could not reinforce fast enough to stem the tide. In one sector the British were throwing 12–15, 000 shells per day at a single division, which was only able to fire 2, 000 back. The Vimy Ridge position was shallow and the defences needed work but the Germans judged that such work was only possible when the weather dried out. The hammering made it obvious that the British were going to attack but they still managed some tactical surprise, possibly because the new 106 impact fuse shortened the period needed for wire-cutting.
The foul weather on 9 April (Easter Monday) also helped the British plan as the SOS flares fired by the front-line German infantry could not be seen in the mist and blowing snow. Progress was therefore excellent on the first day, advancing several miles in some cases, and Vimy Ridge was quickly overrun as well. General Horne would later claim that Vimy had actually been over-bombarded, tearing up the ground and slowing the infantry. That was the flip side of a bombardment that reduced German regiments to battalion strength and filled the survivors with horror:
The enemy had divided up the battlefield like a chessboard. Strip after strip was ploughed and torn up. The entire defensive works were to be demolished and the nerves of the defenders shredded. As it unfolded, it made for dreadful scenes. The explosion of the massive shells ripped great craters out of the earth, sending their contents skyward then, as they fell to ground once more, repeated the process in chaotic confusion.
German batteries might fire up to 1, 500 rounds that day, yet British numbers and planning told, and the Canadians captured over 120 guns, some of them heavies that had been deployed forwards to fire deeper into British lines.
With commendable skill the Germans reorganised during the battle, redeploying to take advantage of greater defence-in-depth, assisted by the BEF’s tendency to launch too-small attacks, a brigade attacking quickly when it would have been safer (and cheaper) – but slower – to send a division. The Germans were actually perplexed by the British operation. Their opponents did not appear to understand how to attack where the ground favoured them, with observers controlling the artillery, but instead insisted on attacking over ridges and hills while relying on a timetabled barrage.
The crisis in the French army apparently caused Haig to prolong the attack. Too often the British would attack an objective their gunners could not see, the infantry would advance over a hill and never be seen again, cut off by German defensive barrages and torn up by German counter-attacks (the Germans also used what they termed mobile artillery – a battery or two attached to counter-attacking battalions – that could offer tactical fire support as long as the British aerial observers did not spot it).9 Before fizzling out in May, the battle for Arras cost the BEF more than the Somme (on a per-day basis) but it had also inflicted significant losses on the Germans as well as wresting Vimy Ridge and a few other observation points out of enemy hands.