Editing Battle of Passchendaele (section)

==Background==

===Flanders===

====1914====

{{further|Belgian Revolution#Belgian neutrality|l1=Belgian neutrality}}

Belgium had been recognised in the [[Treaty of London (1839)]] as a sovereign and neutral state after the secession of the southern provinces of the Netherlands in 1830. The [[German invasion of Belgium (1914)|German invasion of Belgium]] on 4 August 1914, in violation of Article VII of the treaty, was the British {{lang|la|[[casus belli]]}} against Germany.{{sfn|Albertini|2005|pp=414, 504}} British military operations in Belgium began with the arrival of the [[British Expeditionary Force (World War I)|British Expeditionary Force]] (BEF) at [[Mons, Belgium|Mons]] on 22 August. Operations in [[Flanders]] began during the [[Race to the Sea]], reciprocal attempts by the French and German armies to turn their opponents' northern flank, through [[Picardy]], Artois and Flanders. On 10 October, Lieutenant-General [[Erich von Falkenhayn]], the [[German General Staff|Chief of Staff]] of the {{lang|de|[[Oberste Heeresleitung]]}} (OHL, supreme army command), ordered an attack towards Dunkirk and Calais, followed by a turn south behind the Allied armies, to gain a decisive victory.{{sfn|Foley|2007|p=102}} On 16 October, the Belgians and some French reinforcements began the defence of western Belgium and the French [[English Channel|Channel]] ports, at the [[Battle of the Yser]]. When the German offensive failed, Falkenhayn ordered the capture of [[Ypres]] to gain a local advantage. By 18 November, the [[First Battle of Ypres]] had also ended in failure, at a cost of {{nowrap|160,000 German}} casualties.{{sfn|Foley|2007|p=104}} In December, the [[British Admiralty]] began discussions with the [[War Office]], for a combined operation to re-occupy the Belgian coast but were obliged to conform to French strategy and participate in offensives further south.{{sfn|Edmonds|1993|p=2}}

====1915====

Large British offensive operations in Flanders were not possible in 1915, due to a lack of resources.{{sfn|Doughty|2005|p=137}} The Germans conducted their own Flanders offensive at the [[Second Battle of Ypres]] (22 April – 15 May 1915), making the Ypres [[Salients, re-entrants and pockets|salient]] more costly to defend.{{sfn|Edmonds|1993|p=1}} [[Sir Douglas Haig]] succeeded [[John French, 1st Earl of Ypres|Sir John French]] as Commander-in-Chief of the BEF on 19 December.{{sfn|Terraine|1977|pp=12–13}} A week after his appointment, Haig met Rear-Admiral [[Reginald Bacon]], who emphasised the importance of obtaining control of the Belgian coast, to end the threat posed by [[Flanders U-boat flotillas|German U-boats]].{{sfn|Edmonds|1993|p=2}}{{efn|Page 2 of the Official History gives Bacon's rank as Vice-Admiral. His Oxford Dictionary of National Biography article states that he was promoted to this rank late in 1916 and that he was knighted (KCVO) in 1916.}} Haig was sceptical of a coastal operation, believing that a landing from the sea would be far more difficult than anticipated and that an advance along the coast would require so much preparation, that the Germans would have ample warning. Haig preferred an advance from Ypres, to bypass the flooded area around the Yser and the coast, before attempting a coastal attack to clear the coast to the Dutch border.{{sfn|Edmonds|1993|p=2}}

====1916====

{{main|Battle of Verdun|Battle of the Somme}}
{{Campaignbox The Actions of Spring 1916}}

Minor operations took place in the Ypres salient in 1916, some being German initiatives to distract the Allies from their preparations for the offensive at Verdun and later attempts to divert Allied resources from the Battle of the Somme. Other operations were begun by the British to regain territory or to evict the Germans from ground overlooking their positions. Engagements took place on 12 February at Boesinghe and on 14 February at [[Hooge in World War I|Hooge]] and Sanctuary Wood. There were actions from {{nowrap|14 to 15 February}} and {{nowrap|1 to 4 March}} at [[The Bluff, Ypres|The Bluff]], {{nowrap|27 March – 16}} April at the [[Sint-Elooi|St Eloi Craters]] and the [[Battle of Mont Sorrel]] from {{nowrap|2 to 13 June.}}{{sfn|Edmonds|1993|pp=163–245}} In January 1917, the Second Army (General [[Herbert Plumer]]) with the II Anzac, IX, X and VIII corps, held the Western Front in Flanders from Laventie to Boesinghe, with eleven divisions and up to two in reserve. There was much trench mortaring, mining and raiding by both sides and from January to May, the Second Army suffered {{nowrap|20,000 casualties.}} In May, reinforcements began arriving in Flanders from the south; the II Corps headquarters and {{nowrap|17 divisions}} had arrived by the end of the month.{{sfn|Falls|1992|pp=533–534}}

In January 1916, Plumer began to plan offensives against [[Messines Ridge]], [[Lille]] and Houthulst Forest.{{sfn|Edmonds|1993|p=31}} General [[Henry Rawlinson, 1st Baron Rawlinson|Henry Rawlinson]] was also ordered to plan an attack from the Ypres Salient on 4 February; planning continued but the Battle of Verdun and the Battle of the Somme took up the rest of the year.{{sfn|Terraine |1977|pp=14–15}} In November, Haig, the French commander-in-chief [[Joseph Joffre]] and the other Allies met at [[Chantilly Conferences|Chantilly]]. The commanders agreed on a strategy of simultaneous attacks, to overwhelm the [[Central Powers]] on the [[Western Front (World War I)|Western]], [[Eastern Front of World War I|Eastern]] and [[Italian Campaign (World War I)|Italian]] fronts, by the first fortnight of February 1917.{{sfn|Hart|Steel|2001|p=30}} A meeting in London of the Admiralty and the General Staff urged that the Flanders operation be undertaken in 1917 and Joffre replied on 8 December, agreeing to a Flanders campaign after the spring offensive.{{sfn|Falls|1992|p=21}} The plan for a year of [[attrition warfare|attrition]] offensives on the Western Front, with the main effort to be made in the summer by the BEF, was scrapped by the new French Commander-in-Chief [[Robert Nivelle]] in favour of a return to a strategy of decisive battle.{{sfn|Falls|1992|pp=38–39}}

===Allied strategy===

{{see also|Western Front (World War I)|Nivelle Offensive}}

Nivelle planned preliminary offensives to pin German reserves by the British at [[Arras]] and the French between the Somme and the [[Oise]], then a French breakthrough offensive on the [[Aisne (river)|Aisne]], followed by pursuit and exploitation. Haig had reservations and on 6 January Nivelle agreed to a proviso that if the first two parts of the operation failed to lead to a breakthrough, the operations would be stopped and the British could move their forces north for the Flanders offensive, which was of great importance to the British government.{{sfn|Edmonds|Wynne|2010|p=14}} On 23 January, Haig wrote that it would take six weeks to move British troops and equipment to Flanders and on 14 March, noted that the Messines Ridge operation could begin in May. On 21 March, he wrote to Nivelle that it would take two months to prepare the offensive from Messines to Steenstraat but that the Messines operation could be ready in five or six weeks. The main French attack took place from 9 April to 9 May and failed to achieve a breakthrough. On 16 May, Haig wrote that he had divided the Flanders operation into two parts, one to take Messines Ridge and the main attack several weeks later.{{sfn|Terraine|1977|pp=31, 55, 94}} British determination to clear the Belgian coast took on more urgency after the Germans resumed unrestricted submarine warfare on 1 February 1917.{{sfn|Terraine|1999|p=15}} On 1 May 1917, Haig wrote that the Nivelle Offensive had weakened the German army but that an attempt at a decisive blow would be premature.{{sfn|Powell|2004|p=169}} The wearing-out process would continue on a front where the Germans had no room to retreat. Even limited success would improve the tactical situation in the Ypres salient, reducing the exceptional wastage, even in quiet periods.{{sfn|Terraine|1977|p=84}} In early May, Haig set the date for the Flanders offensive, the attack on Messines Ridge to begin on 7 June.{{sfn|Edmonds|1991|p=24}}

===Kerensky offensive===

{{Main|Eastern Front (World War I)|Kerensky Offensive}}

[[File:EasternFront1917.jpg|thumb|upright=.75|{{centre|The Eastern Front in 1917}}]]
The Russian army conducted the Kerensky Offensive in [[Galicia (Eastern Europe)|Galicia]], to honour the agreement struck with the Allies at the Chantilly meeting of 15 to 16 November 1916. After a brief period of success from 1 to 19 July, the Russian offensive was contained by the German and Austro-Hungarian armies, which counter-attacked and forced the Russian armies to retreat. On the [[Baltic Sea|Baltic]] coast from 1 to 5 September 1917, the Germans attacked with their strategic reserve of six divisions and captured [[Riga]]. In [[Operation Albion]] (September–October 1917), the Germans took the [[West Estonian Archipelago|islands]] at the mouth of the [[Gulf of Riga]]. The British and French commanders on the Western Front had to reckon on the German western army ({{lang|de|Westheer}}) being strengthened by reinforcements from the {{lang|de|Ostheer}} on the Eastern Front by late 1917.{{sfn|Edmonds|1991|p=234}} Haig wished to exploit the diversion of German forces in Russia for as long as it continued and urged the British War Cabinet to commit the maximum amount of manpower and munitions to the battle in Flanders.{{sfn|Terraine|1977|pp=290–297}}