There are few words that conjure up more of a sense of dread, loss and futility than Passchendaele, the name by which the Third Battle of Ypres is known. It is second only to the Somme as the largest and bloodiest battle in British history.
The scale of the carnage, with hundreds of thousands of young men killed or wounded, the appalling conditions and the lack of a decisive outcome mean it is impossible to pass the centenary without properly marking it.
On 31 July, I will be out on the battlefield as part of the BBC team covering the commemorations. It is particularly special for me as, like so many others, my great-grandfather was at the battle and his experiences changed him for ever.
The Germans had reached the gates of Ypres in 1914 until heroic defence by British, Indian, Belgian and French troops held them back — just.
The Germans had captured nearly all the high ground, creating the infamous Ypres Salient. By 1917 the largely British troops holding the Salient were in awful, waterlogged trenches. On purely tactical grounds, the British should have abandoned the miserable place.
But war is about politics as much as tactics. This was the last shred of Belgium still occupied by the Allies, the nation for which Britain had marched to war. To sacrifice it now would send a defeatist message to the German High Command and occupied peoples everywhere. So soldiers would drown in mud and die from German snipers because of a politician’s promise.
In the summer of 1917 the German-led central powers had some reasons for optimism. Russia was spiralling into revolution, Turkey was holding its own in the Middle East, German U-boats were exacting a terrible toll on British and Allied shipping in the Atlantic, a massive French offensive had been a catastrophe. Britain had to strike or her coalition of allies might collapse. The Ypres Salient was chosen as the location of a major push — to force the Germans back, make the Salient less intolerable, and begin to threaten the Channel ports from which the German submarines were strangling Britain.
The British were confident. The horrors of the Somme a year before had forged an army of veterans. Kitchener’s volunteers and Pals, those that had survived, were now tough, experienced warriors. New technology was coming into play. Tanks were assembled, new aircraft deployed. The Lewis light machine gun gave the infantry more of a chance against well-fortified German positions.
In June, a limited attack on one ridge, Messines, south of Ypres, prompted talk of a breakthrough. On 31 July 1917 the British attacked the Germans along the north, east and south sides of the Salient. New Zealanders, British and Australian troops captured some key objectives. There were far fewer casualties than the first day of the Somme, when an estimated 20,000 British troops died. In some sectors the advance was as much as 3,000m.
Then on that afternoon the heavens opened. There are those who argue that had it not been for a particularly wet August, the British plan might have worked. But rain it did. Low cloud stopped British planes helping to pinpoint German strongpoints. Tanks got stuck in the mud. Men drowned in water-filled shell holes.
The pitiless logic of the Western Front soon gripped the battlefield. Lacking portable radio sets, advancing troops were unable to ask for help or reinforcement. Horses struggled to pull ungainly artillery pieces through the mud.
It was easier for the Germans to surge in reinforcements across relatively firm ground, on pre-prepared routes, behind their own lines, than for the British to send fresh troops across a smashed battlefield, raked by German gunfire.
Soldiers of the 16th Canadian machine gun regiment using shell holes as makeshift defences at Passchendaele Ridge
During breaks in the weather the British and Empire troops crept forward. At appalling cost they fought to secure the high ground before the winter set in. The final spasm of the assault was in early November by the Canadian troops who eventually seized the village of Passchendaele, about 10km from where the front line had been four months before. To this day it is said that the nation of Canada was born on the field of Passchendaele.
Both sides suffered around 250,000 casualties. It was a terrible disappointment to the British, who had dreamed of breaking out of the trenches, liberating the Belgian coast and striking a crippling blow against the German war machine.
British Prime Minister David Lloyd George later called it “one of the greatest disasters of the war”. But it was an appalling trial for the Germans as well. The stalemate would continue into another year. It became a question of which society, and which army, could tolerate the unprecedented strain.
World War One Remembered: Passchendaele is on Sunday 7.00pm BBC2, Monday 11.00am BBC1