Passchendaele took place on and near the ridgelines south and east of the Belgian city of Ypres (the British Tommies pronounced it 'Yippers'). AKA the Third Battle of Ypres, the campaign opened on 7 June 1917 with the explosion of 19 mines under the German front lines at Messines Ridge south of the Ypres salient. The mines averaged 21 tons of explosives each. They were able to advance two miles on a six mile front,but then bogged down.
By mid-August eyewitness participants described it as “Mud…lice…more mud…noise…jagged steel...horror…men and animals torn to pieces…mud seeded with brains and blood…mud heaving with the putrefying corpses of tens of thousands.”
Sapper John Hunter of the Royal Engineers recalled digging trenches: "It looks like a graveyard I told Jock, who told me just to slice the bodies through at each side of the trench and not to bother digging any more out. The odour was awful and the more we dug the more dead men's bodies we had to go through."
A German general described it as …” worse than Verdun…the greatest martyrdom of the world war.”
It lasted from June to November, but much of it was fought in August. It was actually not a single battle but a five month long campaign comprising at least 12 major battles plus supporting operations. It cost the British Commonwealth at least 244 thousand casualties plus perhaps 140 thousand more French and Belgian. The Russians in the Kerensky Offensive (launched to support Passchendaele) lost 60 thousand. German losses were at least 217 thousand. However, all these casualty figures are disputed.
The campaign included the Battles of Pilckem Ridge, Westhoek, Hill 70, Langemark, Menin Road Ridge, Polygon Wood, Broodeseinde, Poelcappelle, First Passchendaele, La Malmaison, and Second Passchendaele in addition to the opening Battle of Messines Ridge.
At
Pilckem Ridge on 31 July the final Allied artillery barrage just before the attack was
heard in London and throughout southern England.
It was the loudest man-made noise heard on earth (up until that time??). It rivaled the explosion of Krakatoa in
1883. Yet even with that final barrage
and the prior two-weeks of artillery prep, the advance only gained 4000 yards and
was then thrown back by German counterattack.
On 10 August, British II Corps captured Westhoek Ridge but were again thrown back by German counterattack except for one small corner.
Hill 70 in mid-August was fought mainly by the Canadian Corps fresh from the Battle of Vimy Ridge a few months earlier. At the Battle of Hill 70 they were reportedly the first victims of the large scale use of Yperite AKA mustard gas. They may have had gas masks or Hypo helmets as a Canadian Medical Officer is credited as inventing the gas mask after the 1915 chlorine attacks. But were those masks effective against Yperite? 98 years later in August 2015 mustard gas attacks were still happening in Syria and Iraq.
Langemark, also in mid-August was indecisive. The German counterattack retook any earlier gains.
Again in August the French launched the Second offensive battle of Verdun to support the Passchendaele battles. No German counterattack was mounted. Their Eingreif Divisions apparently were busy in Flanders.
It got better for the Brits in September, October, and November. They had developed more effective 'bite and hold' tactics. But even so they never did achieve one of their major goals, which was capturing the U-boat pens on the Belgian seacoast. Total gains were about five miles so they were still 30 miles from Zeebrugge.
The Canucks were also in at the end of the campaign when they captured Passchendaele Ridge in November. What little gains the Brits made during Passchendaele (and arguably the entire war) were due in large part to the sacrifices of Canadians, Australians, New Zealanders, Irish, Scots; Indian Gurkhas, Sikhs, Rajputs, Pashtuns, and Bengalis; as well as South Africans, and Blacks from both East and West Africa and the West Indies.
Field Marshal Douglas Haig AKA Butcher Haig started this bloodbath against the wishes of his Prime Minister, and concealed the start of the campaign until 31 July which was considered the official start. And he also went against against the advice of General Foch who at that time was Chief of the French General Staff and later became Haig's boss as the "Commander-in-Chief (Généralissime) of the Allied Armies". Haig maintained through out the campaign that the casualties were worse on the German side and that attrition was breaking the back of the German 4th Army. Not so apparently. If his intent was to force the Germans to spend lives, they did, but at what cost?. And as the son of a veteran of Passchendaele was quoted as saying: "But if this is generalship, why don't lumberjacks fell oak trees by butting their heads against them?"