The Ypres–Comines railway ran roughly parallel to the roads from Ypres and 600 yd (550 m) from Zillebeke, went through a cutting 15–20 ft (4.6–6.1 m) deep, which extended beyond the crest of the ridge.

On the east side of the cutting, on the highest point of the ridge, was a third mound known as Hill 60, from which observers had an excellent view of the ground around Zillebeke and Ypres.

[a] The hill had been captured on 11 November 1914, by the German 30th Division, during fighting against a mixed force of French and British infantry and cavalry, in the First Battle of Ypres.

[4] The German Imperial Army was a military force drawn from the kingdoms of Prussia, Bavaria, Saxony, Baden and Württemberg.

British infantry began to assemble after dark and 1 Squadron Royal Flying Corps (RFC) was made responsible for keeping German aircraft away from the area.

Débris was flung almost 300 ft (91 m) into the air and scattered for 300 yd (270 m) in all directions, causing some casualties to the attacking battalions of the 13th Brigade of the 5th Division.

Some of the survivors of the 2nd Company ran back in fear that German gas cylinders, earlier placed in the front line, had been ruptured.

The attack was repulsed by British machine-gun fire but on the right, the 8th Company of SIR 105 and pioneers managed to bomb their way close to the craters and dug in under artillery-fire.

Some of the British garrison were able to return fire, which gave enough time for reinforcements to arrive, after rushing through the gas cloud.

The gas hung so thick that even after re-damping cotton respirators, it was impossible to remain in the trenches and those troops who stood their ground were overcome.

German infantry of the 30th Division advanced fifteen minutes after the gas cloud and occupied nearly all of the front line on the lower slope of the hill.

The brigade attacked at 10:00 p.m. after a twenty-minute bombardment but found that the darkness, broken state of the ground and alert German infantry made it impossible to advance, except for one party which reached the top of the hill, only to be forced to withdraw at 1:00 a.m. by enfilade-fire from the Caterpillar and Zwarteleen.

The hill was untenable unless the Caterpillar a considerable amount of ground on the flanks was also occupied; both sides were exhausted and spent the next day digging-in.

At dawn on 7 May, the British attacked the hill with two companies of infantry and attached bombers using hand grenades, all of whom were killed or captured.

By the morning of 18 April, British troops had been pushed back to the near slope but a wireless and signal light station had been established at the headquarters of the 5th Division, to which air observers could report direct.

The 1st Australian Tunnelling Company took over in November 1916, led in part by Captain Oliver Woodward and maintained the mines over the winter.

[d] The blasts created one of the largest explosions in history, reportedly heard in London and Dublin, demolishing a large part of the hill and killing c. 10,000 German soldiers.

The offensive forced the German army to move reserves to Flanders from the Arras and Aisne fronts, which relieved pressure on the French.

Sorrel, led the two infantry brigades of the 23rd Division to advance on either side, up to the near crest of the ridge, arriving while the ground still shook from the mines at Hill 60.

[35] North of the canal, the 47th (1/2nd London) Division had to capture a spoil heap 400 yd (370 m) long, where several German machine-gun nests had been dug in.

The 23rd Division had many casualties caused by flanking machine-gun fire from the spoil heap while clearing Battle Wood, which took until the evening.