Hill 60 was a low rise south-east of Ypres made from the soil removed in digging a cutting for the Ypres to Comines railway. It had excellent views over both Ypres and Zillibeke, and was captured by the Germans during the first Battle of Ypres in November 1914. On 17 April 1915, in one of the first tunnelling operations by the British Army, six mines were exploded under Hill 60, which was then quickly captured with minimal casualties. But, in early May, the Germans recaptured the hill with the use of gas.
In August 1915, 175th Tunnelling Company RE began deep-mining beneath Hill 60. The 3rd Canadian Tunnelling Company completed the task, building two deep chambers. One under Hill 60 was filled with 53,300 pounds of Ammonal explosives; a second branch, under what was known as ‘the Caterpillar’, was filled with 70,000 pounds of explosives. To try to solve the problems of the wet soil, the mines were dug through blue clay 80-120ft below the surface.
In November 1916, the 1st Australian Tunnelling Company commanded by Captain Oliver Woodward took over the tunnels and maintained them through the winter. Eventually there were about 8,000 yards of tunnels in the area. The Germans very nearly discovered the main chambers on more than one occasion.
At 3.10am on 7 June 1917, these two mines and 19 others, containing nearly one million pounds of explosives, were detonated as a prelude to the Battle of Messines. The effect was like that of a particularly violent earthquake. There was a mighty roar, and columns of flame shot into the air. Thousands of tons of rubble, debris, and human remains were scattered over a wide area.
Survivors spoke of a blast of hot air that could be felt 20 miles from the Front. The sound could be heard in London. It is estimated that 10,000 Germans were killed in the explosion. It wrecked the German lines, and provided the Allies with a huge advantage.
Two of the mines did not explode. They were later abandoned, and details of their location were lost. One blew up when hit by lightning in 1955; the other has never been found.