The First Canadian Division was on the right of the Third. The Second Division was farther south at St.-Eloi, and was not called on until later in the action.
The left of the line was held by the Seventh Brigade under Brigadier General A. C. Macdonell and the right by the Eighth Brigade under Brigadier General Victor Williams. Two companies of the Royal Canadian Regiment under Lieutenant Colonel C. H. Hill were astride the Menin road on the far side of Hooge, their left sloping down through bombing posts to link with the British at Bellewaarde Beek, their right in touch with the Princess Patricias at the gap under Lieutenant Colonel Buller. In the southern section of Sanctuary Wood they met the 1st Canadian Mounted Rifles of the Eighth Brigade under Colonel Shaw holding Hills 61 and 62. Next on the right was the 4th Mounted Canadian Rifles under Colonel Ussher holding Mount Sorrel, where the Second Brigade of the First Division continued the line.
Back of the front line there was a support line left of the position. From the Menin road support line trenches extended southeast, held by the support company of the Princess Patricias and the Royal Canadian Regiment. Northeast of Maple Copse, and in the middle of Sanctuary Wood, the support line broke into two systems of trenches. A series of communication trenches broke abruptly back to Maple Copse and the southwest, forming an apex facing the enemy. From the apex the support line continued back of the Canadian front-line trenches on Hill 62 and Mount Sorrel. Fortified posts back of these covered the ground between Zouave Wood and the southern slopes of Observatory Ridge. A second line known as G. H. Q. nearer Ypres was the last defense.
The 5th Canadian Rifles support battalion under Lieutenant Colonel Baker held the fortified post on the north, the 4th Canadian Mounted Rifles the post on the south. The Princess Patricias held one fort. Maple Copse was occupied by a company and a half of the 5th Canadian Mounted Rifles, the 42d Battalion of Royal Highlanders and the remaining company of the Royal Canadian Regiment. The 49th Edmonton Regiment under Lieutenant Colonel Griesbach was the reserve battalion of the Seventh Brigade, and the 2d Canadian Mounted Rifles of the Eighth.
The German offensive on June 2, 1916, was not unexpected, as for some days they had been driving "T" saps in front of their lines and linking them together to form advance trenches.
The German bombardment, which began about 8.30 a. m., surpassed anything of its kind the Canadians had faced since landing on the continent. A tornado of fire and steel swept defenses away. The defenders were slain, or wounded, or buried under débris. The generals and their staffs were caught in the storm. One of the first shells wounded Brigadier General Williams, who was later made a prisoner by the Germans. General Mercer was last seen encouraging his men, and his fate was not known until ten days later when his body, with both legs broken, was found in one of the side trenches. This gallant soldier was buried at Poperinghe, where many other brave Canadian soldiers lie.
The 4th Canadian Mounted Rifles were swept away by the storm of fire, but afterward it was learned that some parties had escaped. The garrison holding the last trench on the right reached the lines of the Second Brigade when night fell.
The German advance was stubbornly resisted. Major Dennison fought a rear-guard action and got back to the second line with five men. The fortified post held by the 4th Canadian Mounted Rifles was blown up. One garrison was wiped out, and only three men got away from the other post. Between thirty and forty men were rallied behind the support line. The casualties were 637.
The 1st Canadian Mounted Rifles Battalion on their left had also met with disaster. Their trenches were obliterated. The survivors retired to the apex, and some on battalion headquarters.
The German attack launched just after 1 o'clock was made in four successive lines from the southwest. Mount Sorrel was reached and the German left flank began clearing the way, when the center attacked the 1st Canadian Mounted Rifles. Colonel Shaw in his redoubt found his right flank exposed, and was attacked on all sides. The garrison fought hard. Colonel Shaw fell and with him Major Palmer and Lieutenant Rowles. At last all the officers but two and most of the noncommissioned officers were killed and wounded. Lieutenants Key and Evans led fifteen survivors back to a fortified post before the apex where, with the help of stragglers, they held out until relieved the next day. The total casualties of the regiment were 367.