Editing Battle of Vimy Ridge (section)

==Prelude==

===Strategy===
{{external media
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| video1 ='''[https://www.historicacanada.ca/productions/minutes/vimy-ridge Vimy Ridge]''' <br>A Canadian [[Heritage Minute]]  that follows [[Major-General Arthur Currie]] discusses the plan of attack on Vimy Ridge with [[General Julian Byng]] – [[Historica Canada]] (1:01 min)
}}

On 28 May 1916, Byng took command of the Canadian Corps from Lieutenant-General Sir [[Edwin Alderson]]. Discussions for a spring offensive near Arras began, following a formal conference of corps commanders held at the [[First Army (United Kingdom)|First Army]] Headquarters (HQ) on 21 November 1916.{{sfn|Nicholson|1962|p=245}} In March 1917, the army HQ formally presented Byng with orders giving Vimy Ridge as the Canadian Corps objective for the Arras Offensive.{{sfn|Brennan|2007|p=94}}

A plan, adopted in early March 1917, drew on the briefings of staff officers sent to learn from the experiences of the French Army during the Battle of Verdun.{{sfn|Brennan|2007|p=94}} For the first time the four Canadian divisions would fight together. The nature and size of the attack needed more resources than the Canadian Corps possessed and the British [[5th Infantry Division (United Kingdom)|5th Division]], artillery, engineer and labour units were attached to the corps, bringing the nominal strength of the Canadian Corps to about 170,000 men, of whom 97,184 were Canadian.{{sfn|Nicholson|1962|p=229}}

===Tactics===
[[File:Plan of Attack Vimy Ridge.jpg|thumb|left|upright|The Canadian Corps plan of attack outlining the four coloured objective lines&nbsp;– Black, Red, Blue and Brown]]
In January 1917, three Canadian Corps officers accompanied other British and Dominion officers attending lectures by the French Army on their experiences during the Battle of Verdun.{{sfn|Brennan|2007|p=94}} The French counter-offensive devised by General [[Robert Nivelle]] had been one of a number of Allied successes of 1916. Following extensive rehearsal, eight French divisions had assaulted German positions in two waves along a {{cvt|6|mi|-1}} front. Supported by extremely powerful artillery, the French had recovered lost ground and inflicted severe casualties on five German divisions.{{sfn|Nicholson|1962|p=227}}

On their return from the lectures, the Canadian Corps staff officers produced a tactical analysis of the Verdun battles and delivered corps and divisional-level lectures to promote the primacy of artillery and stress the importance of harassing fire and company and platoon flexibility.{{sfn|Nicholson|1962|p=227}} The report of the [[1st Canadian Division]] commander, [[Arthur Currie]], highlighted the lessons he believed the Canadian Corps could learn from the experiences of the French.{{sfn|Humphries|2007|p=67}} The final plan for the assault on Vimy Ridge drew on the experience and tactical analysis of the officers who attended the Verdun lectures. The First Army commander, General [[Henry Horne, 1st Baron Horne|Henry Horne]] approved the plan on 5 March 1917.{{sfn|Brennan|2007|p=94}}

[[Image:Julian Byng (April 1917).jpg|upright|thumb|[[Julian Byng, 1st Viscount Byng of Vimy|Byng]] during the battle|alt=Julian Byng in a black and white chest high portrait with foliage behind him. Byng has a moustache and is wearing a general officer's uniform that consists of a tailored jacket adorned with brass buttons. The collar is embellished with additional decorations denoting rank and service branch. He is wearing a peaked cap featuring ornate insignia indicating his rank and unit affiliation.]]
The plan divided the Canadian Corps advance into four coloured objective lines. The attack would be made on a front of {{cvt|7000|yd|mi+km|0}}, with its centre opposite the village of [[Vimy]], to the east of the ridge.{{sfn|Nicholson|1962|p=245}} The first objective, the Black Line, was the German forward defensive position.{{sfn|Granatstein|2004|p=113}} The final objective of the northern flank was the Red Line, taking the highest point on the ridge, the fortified knoll known as the Pimple, la Folie Farm, the {{lang|de|Zwischen-Stellung}} (intermediate position) and the hamlet of Les Tilleuls. The southern two divisions were to achieve two more objectives, the Blue Line, encompassing the village of Thélus and the woods outside the village of Vimy and the Brown Line, which aimed at capturing {{lang|de|Zwölfer-Graben}} (Twelve Trench) and the German second position.{{sfnm|1a1=Granatstein|1y=2004|1p=113|2a1=Nicholson|2y=1962|2p=254}} The infantry would advance close to a [[Barrage (artillery)|creeping barrage]] by field guns, advancing in timed {{cvt|100|yd|-2|adj=on}} increments.{{sfn|Granatstein|2004|p=113}} The medium and heavy [[howitzer]]s would establish a series of standing barrages further ahead of the infantry against defensive positions.{{sfn|Nicholson|1962|p=249}}

The plan called for units to leapfrog as the advance progressed, to maintain momentum during the attack. The initial wave would capture and consolidate the Black Line and then push forward to the Red Line. The barrage would pause for reserve units to move up, then move forward with the units pushing beyond the Red Line to the Blue Line. Once the troops secured the Blue Line, advancing units would once again leapfrog them and capture the Brown Line. Conducted properly, the plan would leave the German forces little time to exit their deep dugouts and defend their positions against the infantry.{{sfn|Turner|2005|p=38}} If the corps maintained its schedule, the troops would advance as much as {{cvt|4000|yd|mi+km}} and have the majority of the ridge under control by 1:00{{spaces|thin}}pm on the first day.{{sfn|Nicholson|1962|p=248}}

===German defences===

[[File:GermanDispositionsatVimy9April1917.jpg|thumb|German dispositions at Vimy Ridge on the first day of the battle{{imagefact|date=December 2022}}]]
The experience of the [[Battle of the Somme]] led the German command to conclude that the policy of rigidly defending a trench position was no longer effective against the firepower that the Entente armies had accumulated.{{sfn|Nicholson|1962|p=239}} Ludendorff published a new defensive doctrine in December 1916, in which deeper defences were to be built, within which the garrison would have room to manoeuvre, rather than rigidly holding successive lines of trenches.{{sfn|Nicholson|1962|p=240}} Along Vimy Ridge, the German forces had spent two years constructing fortifications designed for rigid defence. An extensive network of tunnels and trenches south of Neuville St Vaast was known as "The Labyrinth". Little reconstruction based upon the new [[defence-in-depth]] doctrine had been accomplished by April 1917 because the terrain made it impractical.{{sfn|Wynne|1976|pp=170–171}}

The ridge was {{cvt|700|m}} across at its narrowest point, with a steep drop on the eastern side, all but eliminating the possibility of counterattacks if the ridge was captured.{{sfn|Turner|2005|p=29}}{{sfn|Sheldon|2008|pp=ix, 252}} The Germans were apprehensive about the inherent weakness of the Vimy Ridge defences. Their defensive scheme was to maintain a front line defence of sufficient strength to withstand an initial assault and move operational reserves forward, before the enemy could consolidate their gains or overrun the remaining German positions. The German defence at Vimy Ridge relied largely on the firepower of machine guns.{{sfn|Sheldon|2008|p=252}}

Three divisions, comprising seven infantry regiments were responsible for the immediate defence of the ridge.{{sfn|Godefroy|2007b|p=229}} The paper strength of each division was approximately 15,000 men but their actual strength was significantly lower. In 1917, a full-strength German rifle company was 264 men; at Vimy Ridge, each rifle company contained approximately 150 men.{{sfn|Turner|2005|pp=20–22}} Each German regiment held a zone approximately {{cvt|1000|m|order=flip}} wide, as far back as the rear area. When the Canadian Corps attacked, each German company faced two or more battalions of approximately 1,000 men each.{{sfn|Turner|2005|p=22}} Reserve divisions were kept about {{cvt|15|mi}} back instead of assembling close behind the second line according to the defence-in-depth theory.{{sfn|Nicholson|1962|p=267}}

===Artillery===
[[File:Vimy Ridge 1917-barrage map.jpg|thumb|upright|Map showing rolling artillery barrage for advance]]
The eight field artillery brigades of the Canadian Corps divisional artillery and two heavy artillery groups were reinforced with British artillery units.{{sfn|Farndale|1986|p=238 Map 38}} Four heavy artillery groups, nine field artillery brigades, three divisional artillery groups and the artillery complement of the 5th Division was attached to the Canadian Corps. Ten heavy artillery groups of the flanking I and XVII Corps were assigned tasks in support of the Canadian Corps.{{sfn|Farndale|1986|p=238 Map 38}} The artillery batteries of [[I Corps (United Kingdom)|I Corps]] were particularly important because they enfiladed German gun positions behind Vimy Ridge.{{sfn|Chasseaud|1999|p=266}} The British provided twenty-four brigade artillery groups consisting of four hundred and eighty [[Ordnance QF 18 pounder|18&nbsp;pounder field guns]], one hundred and thirty-eight [[QF 4.5 inch Howitzer|4.5&nbsp;inch howitzers]], ninety-six [[2 inch Medium Mortar|2&nbsp;inch trench mortars]], twenty-four [[9.45 inch Heavy Mortar|9.45&nbsp;inch mortars]], supported by 245 siege guns and heavy mortars.{{sfn|Nicholson|1962|p=225}}{{sfn|Cook|2007|p=113}} This firepower gave a density of one heavy gun for every {{cvt|20|yd|-1|order=flip}} and one field gun for every {{cvt|10|yd|-1|order=flip}} of the corps frontage, representing a considerable average increase, including three times the heavy guns over the distribution of artillery at the Battle of the Somme in 1916.{{sfn|Nicholson|1962|p=225}}{{sfn|Sheffield|2002|pp=191, 194}}

On 8 February, the First Army issued a 3,000-word artillery plan devised by Horne and his principal artillery commander, Major General H. F. Mercer.{{sfn|Robbins|2010|p=164}} Brigadier-General [[Edward Morrison (Canadian Army officer)|Edward Morrison]] developed and issued a 35-page multi-phased fire support plan called ''Canadian Corps Artillery Instruction No.{{spaces}}1 for the Capture of Vimy Ridge'' to support the efforts of the infantry.<ref>WO 106/399 Canadian Corps Artillery Instruction No.&nbsp;1 for the Capture of Vimy Ridge (1917)</ref> The Canadian Corps received three times the artillery normally assigned to a corps for regular operations.{{sfn|Brennan|2007|pp=98–99}} To manage the supply of the extra guns, the Royal Artillery staff officer, Major [[Alan Brooke]], coordinated communication and transport plans to work with the barrage plans.{{sfn|Brennan|2007|pp=98–99}}

A 1.6{{spaces}}million shell allotment allowed the artillery along the Canadian Corps front to maintain a high rate of fire.{{sfn|Cook|2007|p=113}} Improvements in the quality of the shells ensured fewer [[dud]]s.{{sfn|Sheffield|2002|p=191}} The new instantaneous [[No. 106 fuze]] greatly improved the effectiveness of the artillery since this fuse burst reliably with the slightest of contact, unlike older timed fuses, making it especially effective at wire cutting before the advance.{{sfn|Cook|2007|p=113}} To maintain communications during the battle, particularly with the artillery, field units laid over {{cvt|1400|km|order=flip}} of telegraph and [[field telephone]] cabling, normally at a depth of {{cvt|7|ft}}.{{sfn|Turner|2005|p=39}} The corps conducted coordinated [[counter-battery]] shoots before the battle. The First Army Field Survey Company printed barrage maps for all batteries, produced artillery boards and provided counter-battery support with their flash spotting groups and [[sound ranging]] sections.{{sfn|Chasseaud|1999|p=268}} Using flash spotting, sound ranging and aerial reconnaissance from [[No. 16 Squadron RAF|16 Squadron]] and {{nowrap|1 & 2}} Balloon Companies [[Royal Flying Corps]] (RFC) in the week before the battle, the counter-battery artillery under command of Lieutenant-Colonel [[Andrew McNaughton]] fired 125,900 shells, harassing an estimated 83 per cent of the German gun positions.{{sfn|Cook|2007|p=117}}

===Training===
[[File:Model reproduction of German lines.jpg|thumb|Large model of German trench lines|alt=a vast full-scale model of the Vimy Ridge battlefield sprawls out across the landscape, resembling a football field in size. The intricate details of the terrain, including trenches, craters, and rough terrain, are meticulously recreated, providing a vivid representation of the historic battleground. Along the periphery of the model, soldiers stand, their figures adding a human dimension to the scene. The soldiers' presence shows the scale of the battlefield model.]]
In February 1917, the British General Staff released a training pamphlet ''SS 143 Instructions for the Training of Platoons for Offensive Action'', espousing the return to the pre-war emphasis on [[fire and movement]] tactics and the use of the [[platoon]] as the basic tactical unit.{{sfn|Corkerry|2001|loc=all}} The pamphlet noted the importance of specialist hand grenade, rifle grenade, rifle and [[Lewis gun]] sections in suppressing enemy strong points by exploiting the characteristics of different weapons to fight forward, allowing other units to advance.{{sfn|Turner|2005|p=38}} Coupled with the observations and suggestions made by Currie in the report he submitted in January 1917 following the Verdun lectures, the Canadian Corps instilled the tactical change with vigour.{{sfn|Humphries|2007|pp=73–76}} The corps implemented the tactical doctrine for small units by assigning objectives down to the platoon. Assaulting infantry battalions used hills behind the lines as full-scale models of the battlefield.{{sfn|Turner|2005|p=39}}

Taped lines demarcated German trench lines while officers on horseback carried flags to represent the advancing front of the artillery barrage.{{sfn|Nicholson|1962|p=227}} Recognizing that leaders were likely to be wounded or killed, soldiers learned the jobs of those beside and above them. At the First Army headquarters, a large [[plasticine]] model of the Vimy sector was constructed and used to show commissioned and senior non-commissioned officers the topographical features of the battlefield and details of the German trench system.{{sfn|Turner|2005|p=39}} Upwards of 40,000 topographical [[trench map]]s were printed and distributed to ensure that even platoon sergeants and section commanders possessed a wider awareness of the battlefield.{{sfn|Humphries|2007|p=77}} The new measures gave each platoon a clearer picture of how it fitted into the greater battle plan and in so doing, reduced the [[Command and control (military)|command]] problems that plagued First World War operations.{{sfn|Barris|2007|p=41}}{{sfn|Terraine|1992|p=180}}

===Underground operations===

[[File:World War I - Vimy sector tunnel.jpg|thumb|British-dug fighting tunnel in Vimy sector|alt=A narrow first World War fighting tunnel carved through chalk is depicted. The tunnel, roughly the height of a person, is illuminated by the white of the chalk, casting shadows along its walls. On the floor, there is rubble pilled to one side. The rough-hewn walls bear marks of manual excavation.]]
Operations along the Vimy Ridge were accompanied by extensive excavations. The Arras–Vimy sector was conducive to tunnelling, owing to the soft, porous, yet extremely stable nature of the [[chalk]] underground. Mine warfare had been conducted on the Vimy sector since 1915 and Bavarian engineers had blown twenty mines in the sector by March 1915.{{sfn|Sheldon|2008|pp=177–179}} By early 1916, German miners had gained an advantage over their French counterparts.{{sfn|Sheldon|2008|p=225}} British [[tunnelling companies of the Royal Engineers]] took over from the French between February and May 1916.<ref name="durandvimy">{{cite web |author=<!--Staff writer(s); no by-line.--> |website=The Durand Group |title=Vimy Ridge |url=http://www.durandgroup.org.uk/durand_group_vimy_ridge.html |access-date=3 August 2016 |archive-date=26 October 2016 |archive-url=https://web.archive.org/web/20161026172817/http://www.durandgroup.org.uk/durand_group_vimy_ridge.html |url-status=live }}</ref>

On their arrival, the British began offensive mining against German miners, first stopping the German underground advance and then developing a defensive strategy that prevented the Germans from gaining a tactical advantage by mining.<ref name="durandvimy"/>{{sfn|Sheldon|2008|p=225}} From spring 1916, the British had deployed five tunnelling companies along the Vimy Ridge and during the first two months of their tenure of the area, 70 mines were fired, mostly by the Germans.{{sfn|Jones|2010|p=133}} Between October 1915 and April 1917 an estimated 150 French, British and German charges were fired in this {{cvt|7|km|mi|order=flip}} sector of the Western Front.<ref name="durandvimy"/> In May 1916, [[The German Attack on Vimy Ridge, 21 May 1916|Operation Schleswig-Holstein]], a German infantry attack, forced the British back {{cvt|700|yd|m}}, to stop British mining by capturing the shaft entrances. In the second half of 1916, the British constructed strong defensive underground positions and from August 1916, the Royal Engineers developed a mining scheme for a big infantry attack on the Vimy Ridge proposed for autumn 1916, although this was postponed.{{sfn|Jones|2010|p=133}} After September 1916, when the Royal Engineers had completed their network of defensive galleries along most of the front line, offensive mining largely ceased although activities continued until 1917. The British gallery network beneath Vimy Ridge eventually grew to a length of {{cvt|12|km|mi|order=flip}}.<ref name="durandvimy"/>

The Canadian Corps was posted to the northern part of Vimy Ridge in October 1916 and preparations for an attack were revived in February 1917.{{sfn|Jones|2010|p=133}} Twelve [[Subway (underpass)|subways]], up to {{cvt|1.2|km}} long were excavated at a depth of {{cvt|10|m}} and used to connect reserve lines to front lines, permitting soldiers to advance to the front quickly, securely and unseen. Often incorporated into subways were light rail lines, hospitals, command posts, water reservoirs, ammunition stores, mortar and machine gun posts and communication centres.{{sfn|Barton|Doyle|Vandewalle|2004|p=200}} The Germans dug a number of similar tunnels on the Vimy front, to provide covered routes to the front line and protection for headquarters, resting personnel, equipment, and ammunition.{{sfn|Sheldon|2008|p=200}}{{refn|These included the {{lang|de|Prinz Arnulf, Volker}} and {{lang|de|Schwaben}} tunnels.{{sfn|Robinson|Cave|2011|p=60}} |group="Note"}} The Germans also conducted [[counter-mine|counter-mining]] against the British tunnellers and destroyed a number of British attempts to plant mines under or near their lines.{{sfn|Sheldon|2008|pp=218–222}}{{refn|German counter-mining explosion; {{cvt|35|t}} exploded near the Broadmarsh Crater (creating the Longfellow crater group) on 23 March 1917, {{cvt|45|t}} exploded 26 March 1917 near the Pimple.|group="Note"}}

Prior to the battle, the British tunnelling companies secretly laid 13 mines under German positions, to destroy surface fortifications before the assault.{{sfn|Boire|1992|pp=22–23}}<ref name="durandvimy"/> To protect some advancing troops from German machine gun fire as they crossed no man's land during the attack, eight smaller ''Wombat'' charges were laid at the end of the subways to allow troops to move more quickly and safely enter the German trench system by creating an elongated trench-depth crater that spanned the length of no man's land.<ref name="durandvimy"/> At the same time, 19 crater groups existed along this section of the Western Front, each with several large craters.{{sfn|Boire|1992|p=20}} To assess the consequences of infantry having to advance across cratered ground after a mining attack, officers from the Canadian Corps visited [[La Boisselle]] and [[Fricourt]] where the [[Mines on the first day of the Somme|mines]] had been blown on the [[First day of the Somme]]. Their reports and the experience of the Canadians at [[The Actions of St Eloi Craters]] in April 1916, where mines had so altered and damaged the landscape as to render occupation of the mine craters by the infantry all but impossible, led to the decision to remove offensive mining from the central sector allocated to the Canadian Corps at Vimy Ridge. Further British mines in the area were vetoed following the blowing by the Germans on 23 March 1917 of nine craters along [[no man's land]] as it was probable that the Germans were aiming to restrict an  attack to predictable points. The three mines laid by [[172nd Tunnelling Company]] were also dropped from the British plans. The mines were left in place after the assault and were only removed in the 1990s.{{sfn|Jones|2010|pp=134–135}} Another mine, prepared by [[176th Tunnelling Company]] against the German strongpoint known as the Pimple, was not completed in time for the attack. The gallery had been pushed silently through the clay, avoiding the sandy and chalky layers of the Vimy Ridge but by 9 April 1917 was still {{cvt|70|ft|order=flip}} short of its target.{{sfn|Jones|2010|p=136}} In the end, two mines were blown before the attack, while three mines and two ''Wombat'' charges were fired to support the attack, including those forming a northern flank.<ref name="durandvimy"/>{{sfn|Jones|2010|p=135}}

===Trench raiding===
{{details|Trench raiding}}
Trench raiding involved making small-scale surprise attacks on enemy positions, often in the middle of the night for reasons of stealth. All belligerents employed trench raiding as a tactic to harass their enemy and gain [[Military intelligence|intelligence]].{{sfn|Cook|1999|p=10}} In the Canadian Corps trench raiding developed into a training and leadership-building mechanism.{{sfn|Cook|1999|p=10}} The size of a raid would normally be anything from a few men to an entire company, or more, depending on the size of the mission.{{sfn|Tucker|1996|p=694}} The four months before the April attack saw the Canadian Corps execute no fewer than 55 separate trench raids.{{sfn|Cook|1999|p=10}} Competition between units even developed with units competing for the honour of the greatest number of prisoners captured or most destruction wrought.{{sfn|Turner|2005|p=41}} The policy of aggressive trench raiding was not without its cost. A large-scale trench raid on 13 February 1917, involving 900 men from the [[4th Canadian Division]], resulted in 150 casualties.{{sfn|Sheldon|2008|p=xi}} An even more ambitious trench raid, using chlorine gas, on 1 March 1917, once again by the 4th Canadian Division, failed and resulted in 637 casualties including two battalion commanders and a number of company commanders killed.{{sfn|Sheldon|2008|p=xi}}{{sfn|Cook|1999|pp=7–24}} This experience did not lessen the extent to which the Canadian Corps employed trench raiding with raids being conducted nightly between 20 March and the opening of the offensive on 9 April, resulting in approximately 1,400 additional Canadian casualties.{{sfn|Sheldon|2008|p=xi}}{{sfn|Turner|2005|pp=41–42}} The Germans operated an active patrolling policy and although not as large and ambitious as those of the Canadian Corps, they also engaged in trench raiding. As an example, a German trench raid launched by 79 men against the 3rd Canadian Division on 15 March 1917 was successful in capturing prisoners and causing damage.{{sfn|Sheldon|2008|p=254}}

===Air operations===
{{see also|Royal Flying Corps|Luftstreitkräfte}}

[[File:RFC aircraft with aerial reconnaissance camera.jpg|thumb|Observer of the Royal Flying Corps in a photographic reconnaissance aircraft, showing the camera|alt=a military member is seated in the observer's cockpit of a Royal Flying Corps plane. The emblem of the Royal Flying Corps is prominently displayed on the side of the aircraft. The military member is seen adjusting a camera mounted to the side of the fuselage, positioned just behind the wing.]]
The RFC launched a determined effort to gain air superiority over the battlefield in support of the spring offensive. The Canadians considered activities such as artillery observation and photography of opposing trench systems, troop movements and gun emplacements essential to continue their offensive.{{sfn|Barris|2007|p=49}} The Royal Flying Corps deployed 25 squadrons totalling 365 aircraft along the Arras sector, outnumbering the {{lang|de|[[Luftstreitkräfte]]}} (Imperial German Air Service) by 2-to-1.{{sfn|Barris|2007|p=49}} Byng was given use of [[No. 2 Squadron RAF|No. 2 Squadron]], [[No. 208 Squadron RAF|No. 8 (Naval) Squadron]], [[No. 25 Squadron RAF|No. 25 Squadron]], [[No. 40 Squadron RAF|No. 40 Squadron]] and [[No. 43 Squadron RAF|No. 43 Squadron]], with No. 16 Squadron permanently attached to the Canadian Corps and employed exclusively for reconnaissance and artillery-observation.{{sfn|Turner|2005|p=43}}

Aerial reconnaissance was often a hazardous task because of the necessity of flying at slow speeds and low altitudes. The task was made more dangerous with the arrival of German air reinforcements, including the highly experienced and well-equipped [[Jasta 11]] which led to a sharp increase in RFC losses. Although significantly outnumbering the Germans, the RFC lost 131 aircraft during the first week of April ([[Bloody April]]).{{sfn|Turner|2005|p=43}} Despite the losses suffered by the RFC, the {{lang|de|Luftstreitkräfte}} failed to prevent the British from carrying out its priority, air support of the army during the Battle of Arras with up-to-date aerial photographs and other reconnaissance information.{{sfn|Barris|2007|p=49}}