Battle of Passchendaele - Background

Background

The Treaty of London (1839) recognized Belgium as an independent and neutral state. The German invasion of Belgium on 4 August 1914, in violation of Article VII of the treaty, was the reason given by the British government for declaring war. British military operations in Belgium began with the arrival of the British Expeditionary Force (BEF) at Mons on 22 August. On 16 October the Belgians, with some French reinforcements, began the defence of the French channel ports and what remained of unoccupied Belgium at the Battle of the Yser. Operations further south in Flanders commenced, after attempts by the French and German armies to turn their opponents' northern flank through Picardy, Artois and Flanders, (the 'Race to the Sea') reached Ypres. On 10 October Lieutenant-General Erich von Falkenhayn, Chief of the General Staff ordered an attack towards Dunkirk and Calais followed by a turn south to gain a decisive victory. When the offensive failed Falkenhayn ordered the capture of Ypres to gain a local advantage. By 12 November the First Battle of Ypres had failed (at a cost of 160,000 German casualties) and was stopped on 18 November.

In December 1914 the Admiralty began discussions with the War Office for a combined operation to occupy the Belgian coast to the Dutch frontier, by an attack along the coast combined with a landing at Ostend. In the event the British were obliged to participate in the French offensives further south. Large British offensive operations in Flanders were not possible later in 1915, due to shortages of everything. In the event the Germans conducted a Flanders offensive at Ypres (22 April – 15 May 1915), making the Ypres salient more costly and harder to defend. Sir Douglas Haig succeeded Sir John French as Commander-in-Chief of the BEF on 19 December 1915. A week after his appointment Haig met Vice-Admiral Sir Reginald Bacon, who emphasised the importance of obtaining control of the Belgian coast, to end the threat from there by German naval forces. Haig was sceptical of a coast 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 a coastal attack was attempted, to clear the coast to the Dutch border.

In January 1916 Haig ordered General Plumer to plan offensives against Messines Ridge, Lille and Houthoulst Forest. General Rawlinson was also ordered to plan an attack from the Ypres Salient on 4 February. Planning by Plumer continued but the demands of the Battles of Verdun and the Somme absorbed the offensive capacity of the British Expeditionary Force. On 15 and 29 November 1916, as the Battle of the Somme paused, Haig met Général d'Armée Joffre and the other Allies at Chantilly. An offensive strategy to overwhelm the Central Powers was agreed, with attacks planned on the Western, Eastern and Italian Fronts, by the first fortnight in February 1917. A meeting in London of the Admiralty and General Staff urged that the Flanders operation be undertaken in 1917 and Joffre replied on 8 December agreeing to the proposal for a Flanders campaign after the spring offensive. The plan for a year of steady attrition on the Western Front, with the main effort in the summer being made by the British Expeditionary Force, was scrapped by Nivelle and the French government for a decisive battle, to be conducted in February by the French army, with the British army's contribution becoming a preliminary operation, the Battles of Arras.

Nivelle planned an operation in three parts, preliminary offensives to pin German reserves by the British at Arras and the French between the Somme and the Oise, a French breakthrough offensive on the Aisne, then pursuit and exploitation. The plan was welcomed by Haig with reservations, which he addressed on 6 January. After repeated insistence on Haig's part, Nivelle agreed to a proviso that if the first two parts of the operation failed to lead to part three, they would be stopped so that the British could move their main forces north for the Flanders offensive, which Haig argued was of great importance to the British government. Haig wrote on 23 January that it would take six weeks to move British troops and equipment from the Arras front to Flanders and on 14 March he noted that the attack on Messines Ridge could be made in May. On 21 March he wrote to Nivelle that it would take two months to prepare the attacks from Messines to Steenstraat but that the Messines attack could be ready in 5–6 weeks. On 16 May Haig wrote that he had divided the Flanders operation into two phases, one to take Messines Ridge and the main attack several weeks later. British determination to clear the Belgian coast took on more urgency after the Germans resumed unrestricted submarine warfare on 1 February 1917.

Small operations took place in the Ypres salient in 1916, some being German initiatives to distract the Allies from the preparations for the offensive at Verdun and later to try to divert Allied attention 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 Boesinge and on 14 February at Hooge and Sanctuary Wood. There were actions on 14–15 February and 1–4 March at The Bluff, 27 March – 16 April at the St Eloi Craters and the battle of Mount Sorrel 2–13 June. In January 1917 the Second Army (II Anzac, IX, X and VIII corps) held the line in Flanders from Laventie to Boesinghe, with 11 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 had 20,000 casualties. In May reinforcements began moving to Flanders from the south, II Corps and 17 divisions had arrived by the end of the month.