Editing Battle of the Somme (section)

== Strategic developments ==
[[File:Western front 1915-16.jpg|thumb|upright=1.4|{{center|The Western Front 1915–1916}}]]

Allied war strategy for 1916 was decided at the [[Chantilly Conferences|Chantilly Conference]] from 6th to 8th December 1915. Simultaneous offensives on the [[Brusilov Offensive|Eastern Front]] by the Russian army, on the [[Italian Front (World War I)|Italian Front]] by the Italian army and on the [[Western Front (World War I)|Western Front]] by the Franco-British armies were to be carried out to deny time for the [[Central Powers]] to move troops between fronts during lulls. In December 1915, General Sir [[Douglas Haig, 1st Earl Haig|Douglas Haig]] replaced Field Marshal Sir [[John French, 1st Earl of Ypres|John French]] as Commander-in-Chief of the BEF. Haig favoured a British offensive in Flanders, close to BEF supply routes, to drive the Germans from the [[North Sea|Belgian coast]] and end the [[U-boat]] threat from Belgian waters. Haig was not formally subordinate to [[Marshal of France|Marshal]] [[Joseph Joffre]] but the British played a lesser role on the Western Front and complied with French strategy.{{sfn|Hart|2006|pp=27–37}}

In January 1916, Joffre had agreed to the BEF making its main effort in Flanders but in February 1916 it was decided to mount a combined offensive where the French and British armies met, astride the Somme River in [[Picardy]] before the British offensive in Flanders.{{sfn|Hart|2006|p=37}} A week later the Germans began the [[Battle of Verdun]] against the French army. The costly defence of Verdun forced the army to divert divisions intended for the Somme offensive, eventually reducing the French contribution to {{nowrap|13 divisions}} in the [[Sixth Army (France)|Sixth Army]], against {{nowrap|20 British}} divisions.{{sfn|Doughty|2005|p=291}} By 31 May, the ambitious Franco-British plan for a decisive victory had been reduced to a limited offensive to relieve pressure on the French at Verdun and inflict attrition on the German armies in the west.{{sfn|Philpott|2009|pp = 81, 86}}

The Chief of the [[German General Staff]], [[Erich von Falkenhayn]], intended to end the war by splitting the Anglo-French Entente in 1916, before its material superiority became unbeatable. Falkenhayn planned to defeat the large number of reserves which the Entente could move into the path of a breakthrough, by threatening a sensitive point close to the existing [[front line]] and provoking the French into counter-attacking German positions. Falkenhayn chose to attack towards Verdun to take the [[Meuse]] heights and make Verdun untenable. The French would have to conduct a counter-offensive on ground dominated by the German army and ringed with masses of heavy artillery, leading to huge losses and bringing the French army close to collapse. The British would mount a hasty relief offensive and suffer similar losses. Falkenhayn expected the relief offensive to fall south of [[Arras]] against the 6th Army and be destroyed. (Despite the certainty by mid-June of an Anglo-French attack on the Somme against the [[2nd Army (German Empire)|2nd Army]], Falkenhayn sent only four divisions, keeping eight in the western strategic reserve. No divisions were taken from the Sixth Army, despite it holding a shorter line with {{frac|17|1|2}} divisions and three of the divisions in OHL reserve behind the 6th Army. The maintenance of the strength of the 6th Army, at the expense of the 2nd Army on the Somme, indicated that Falkenhayn intended the counter-offensive against the British to be made north of the Somme front, once the British offensive had been shattered.{{sfn|Foley|2007|pp=248–249}}) If such Franco-British defeats were not enough, Germany would attack the remnants of both armies and end the western alliance for good.{{sfn|Foley|2007|pp = 206–207}} The unexpected length of the Verdun offensive, and the need to replace many drained units at Verdun, depleted the German strategic reserve placed behind the 6th Army, which held the Western Front from [[Hannescamps]], {{convert|18|km|mi|abbr=on}} south-west of Arras to [[Sint-Elooi|St Eloi]], south of [[Ypres]] and reduced the German counter-offensive strategy north of the Somme to one of passive and unyielding defence.{{sfn|Wynne|1976|p = 104}}

=== Battle of Verdun ===
{{Main|Battle of Verdun}}

The Battle of Verdun ({{nowrap|21 February – 16
}} December 1916) began a week after Joffre and Haig agreed to mount an offensive on the Somme. The German offensive at Verdun was intended to threaten the capture of the city and induce the French to fight an attrition battle, in which German advantages of terrain and firepower would cause the French disproportionate casualties. The battle changed the nature of the offensive on the Somme, as French divisions were diverted to Verdun, and the main effort by the French diminished to a supporting attack for the British. German overestimation of the cost of Verdun to the French contributed to the concentration of German infantry and guns on the north bank of the Somme.{{sfn|Sheffield|2003|pp = 18–19}} By May, Joffre and Haig had changed their expectations of an offensive on the Somme, from a decisive battle to a hope that it would relieve Verdun and keep German divisions in France, which would assist the Russian armies conducting the Brusilov Offensive. The German offensive at Verdun was suspended in July, and troops, guns, and ammunition were transferred to Picardy, leading to a similar transfer of the French Tenth Army to the Somme front. Later in the year, the Franco-British were able to attack on the Somme and at Verdun sequentially and the French recovered much of the ground lost on the east bank of the Meuse in October and December.{{sfn|Philpott|2009|pp = 412–413}}

=== Brusilov offensive ===
{{main|Brusilov offensive}}
[[File:Indian bicycle troops Somme 1916 IWM Q 3983.jpg|thumb|right|{{center|Troops of the [[British Indian Army]] at Battle of the Somme.}}]]

The Brusilov offensive ({{nowrap|4 June – 20 September}}) on the [[Eastern Front (World War I)|Eastern Front]] absorbed the extra forces that had been requested on 2 June by [[Fritz von Below]], commanding the German Second Army, for a spoiling attack on the Somme. On 4 June, Russian armies attacked on a {{convert|200|mi|km|adj=on|abbr=on}} front, from the Romanian frontier to Pinsk and eventually advanced {{convert|150|km|mi|order=flip|abbr=on}}, reaching the foothills of the Carpathian mountains, against German and Austro-Hungarian troops of {{lang|de|Armeegruppe von Linsingen}} and {{lang|de|Armeegruppe Archduke Joseph}}. During the offensive the Russians inflicted {{circa|1,500,000 losses}} including {{circa|407,000 prisoners}}.{{sfn|Dowling|2008|pp = xv, 163}} Three divisions were ordered from France to the Eastern Front on 9 June and the spoiling attack on the Somme was abandoned. Only four more divisions were sent to the Somme front before the Anglo-French offensive began, bringing the total to {{frac|10|1|2}} divisions. Falkenhayn, and then Hindenburg and Ludendorff, were forced to send divisions to Russia throughout the summer to prevent a collapse of the Austro-Hungarian army and then to conduct a counter-offensive against [[Romania during World War I|Romania]], which declared war against the Central Powers on 27 August.{{sfn|Sheffield|2003|p = 27}} In July there were {{nowrap|112 German}} divisions on the Western Front and {{nowrap|52 divisions}} in Russia and in November there were {{nowrap|121 divisions}} in the west and {{nowrap|76 divisions}} in the east.{{sfn|Miles|1992|p = 555}}

=== Tactical developments ===
[[File:The Battle of the Somme, July-november 1916 Q724.jpg|thumb|right|{{center|Men of the 10th (Service) Battalion, [[East Yorkshire Regiment]] of the [[31st Division (United Kingdom)|31st Division]] marching to the front line, 28 June 1916.}}]]

The original [[British Expeditionary Force (World War I)|British Expeditionary Force]] (BEF) of 6 [[division (military)|divisions]] and the Cavalry Division, had lost most of the British pre-war regulars in the battles of 1914 and 1915. The bulk of the army was made up of volunteers of the [[Territorial Force]] and [[Kitchener's Army]], which had begun forming in August 1914. Rapid expansion created many vacancies for senior commands and specialist functions, which led to many appointments of retired officers and inexperienced newcomers. In 1914, Douglas Haig had been a [[Lieutenant-general (United Kingdom)|lieutenant-general]] in command of [[I Corps (United Kingdom)|I Corps]] and was promoted to command the [[First Army (United Kingdom)|First Army]] in early 1915 and then the BEF in December, which eventually comprised five armies with sixty divisions. The swift increase in the size of the army reduced the average level of experience within it and created an acute equipment shortage. Many officers resorted to directive command to avoid delegating to novice subordinates, although divisional commanders were given great latitude in training and planning for the attack of 1 July, since the heterogeneous nature of the 1916 army made it impossible for corps and army commanders to know the capacity of each division.{{sfn|Simpson|2005|p = 34}}

Despite considerable debate among German [[Staff (military)|staff officers]], Erich von Falkenhayn continued the policy of unyielding defence in 1916. Falkenhayn implied after the war that the psychology of German soldiers, shortage of manpower and lack of reserves made the policy inescapable, as the troops necessary to seal off breakthroughs did not exist. High losses incurred in holding ground by a policy of no retreat were preferable to higher losses, voluntary withdrawals and the effect of a belief that soldiers had discretion to avoid battle. When a more flexible policy was substituted later, decisions about withdrawal were still reserved to army commanders.{{sfn|Sheldon|2006|p=223}} On the Somme front, Falkenhayn's construction plan of January 1915 had been completed. Barbed wire obstacles had been enlarged from one belt {{convert|5|–|10|yd|m}} wide to two, {{convert|30|yd|m}} wide and about {{convert|15|yd|m}} apart. Double and triple thickness wire was used and laid {{convert|3|–|5|ft|m}} high. The front line had been increased from one trench line to a position of three lines {{convert|150|–|200|yd|m}} apart, the first trench ({{lang|de|Kampfgraben}}) occupied by sentry groups, the second ({{lang|de|Wohngraben}}) for the bulk of the front-trench garrison and the third trench for local reserves. The trenches were [[Traverse (trench warfare)|traversed]] and had sentry-posts in concrete recesses built into the [[parapet]]. Dugouts had been deepened from {{convert|6|–|9|ft|m}} to {{convert|20|–|30|ft|m}}, {{convert|50|yd|m}} apart and large enough for {{nowrap|25 men}}. An intermediate line of strongpoints (the {{lang|de|Stützpunktlinie}}) about {{convert|1000|yd|m}} behind the front line was also built. Communication trenches ran back to the reserve line, renamed the second position, which was as well-built and wired as the first position. The second position was beyond the range of Allied field artillery, to force an attacker to stop and move field artillery forward before assaulting the position.{{sfn|Wynne|1976|pp = 100–101}}