Mont Sorrel is not a mountain. It is a slow Belgian rise, a few hundred yards across, on a ridge that runs through Hooge and Zwarteleen east of Ypres. With its neighbours Tor Top (Hill 62) and Hill 61, it stood about thirty metres above the swampy ground at Zillebeke. By spring 1916 it was the last fragment of the high ground around Ypres that the Allies still held. From its crest, a soldier could see the cathedral spires of Ypres four kilometres away, and the German army could see, in the other direction, every road and railway that fed the British rear. Both sides knew it mattered. The Canadians, newly arrived in the salient and still finding their feet, were the ones holding it.

The Germans needed a diversion. The British and French were assembling on the Somme for what would become the great summer offensive, and the German Supreme Command, exhausted by Verdun, could spare nothing for a major counter-stroke. The XIII (Royal Wurttemberg) Corps, commanded by General von Watter, was told to take Mont Sorrel and the heights beside it to draw British attention north. They spent six weeks preparing in secret, telling their troops they were being transferred away, slowly extending forward saps and stockpiling guns and trench mortars. On 1 June the men were finally told what was coming. They were also told, by way of encouragement, that the Imperial Navy had just won a great victory at Jutland. They climbed into the assault trenches that night. The two battalions of Infantry Regiment 121 facing the 8th Canadian Brigade had been raised in Ulm and the Swabian Alps; they were carpenters and Lutheran farmers' sons, mostly, doing what they had been ordered to do.

On the morning of 2 June, the Wurttemberg corps opened the heaviest bombardment the Canadian Corps had yet faced. Nine-tenths of the Canadian forward reconnaissance battalion became casualties before the German infantry even moved. At one o'clock in the afternoon, German pioneers detonated four mines under the Canadian trenches, and six battalions stormed forward through the smoke. Resistance at the front line was, in the official history's bleak word, minimal. The 4th Canadian Mounted Rifles, dismounted infantry from Manitoba and the West, were almost annihilated in their trenches. The Princess Patricia's Canadian Light Infantry, on the left, lost more than four hundred men holding Sanctuary Wood while their flank gave way. The Germans took Mont Sorrel, Tor Top and Hill 61 within a few hours. The road to Ypres lay open, but no German officer pushed past the limits in his orders, and the moment closed.

Julian Byng, the new Canadian Corps commander, threw together a counter-attack in the early hours of 3 June. It was hurried, badly coordinated, and largely failed in broad daylight, with four battalions advancing into machine-gun fire across open ground. So Byng stopped, and waited, and gave the job of the deliberate counter-attack to Arthur Currie, commander of the 1st Canadian Division. Currie was a former real-estate agent from Victoria, British Columbia, and he was about to become one of the war's most respected divisional and corps commanders. He spent six days preparing. From 9 to 12 June he ran four short, deceptive thirty-minute bombardments to make the Germans expect immediate attacks that never came. On 12 June he kept all the German positions between Hill 60 and Sanctuary Wood under fire for ten hours. At dawn on 13 June, after another forty-five minutes of intense shelling, the Canadian battalions went forward behind a smoke screen. Two hundred German prisoners were taken. In just over an hour, the original Canadian line was back in Canadian hands.

From 2 to 14 June, the Canadian Corps lost 8,430 men killed, wounded and missing. The German Wurttemberg divisions and the 117th Division together suffered 5,765. The dead lie in the small cemeteries that ring the ridge today: Sanctuary Wood, Hooge Crater, Maple Copse, Lijssenthoek. Those whose bodies were never found are listed on the Menin Gate in Ieper, eleven kilometres west. After the battle, Byng refused to let the politician Sam Hughes appoint his own son to the vacant divisional command, and promoted Louis Lipsett instead, infuriating Ottawa and saving lives. Quietly, in the same weeks, the unreliable Canadian Ross rifle began to be replaced with the British Lee-Enfield. Mont Sorrel was the Canadian Corps' first major action, a victory of sorts in the end, paid for by men in their twenties from Calgary and Winnipeg and Trois-Rivieres. A small stone on Observatory Ridge marks where the 15th Battalion fought. The ridge itself is hardly thirty metres high. From the top, in the long Belgian dusk, you can still see Ypres.