Caterpillar Crater was formed by a mine exploded under the German position on high ground south of the Ypres- Comines railway. Hill 60 and the "Caterpillar" would be the northern section of the mine battle on June 7, 1917. The Caterpillar was the name coined for the meandering hill on the south side of the railway. On aerial photographs the shape of the hill top at this time resembled a caterpillar, hence the name.
The preparation for placing the mines under the two hills began in August 1915, when beginning the excavation of the so-called "Berlin Tunnel" 'from behind the British lines, first through the '175th Tunnelling Company', from April 1916 through the '3rd Canadian Tunnelling Company'. They started in the already dug gallery to dig toward Hill 60 ("Hill 60 A') with a split going Caterpillar ('Hill 60 B'). The mine charge under Hill 60 was finally placed in July 1916 (24.290 kg of explosives at a depth of 27.4 m), those under the Caterpillar in October 1916 (31.780 kg of explosives at a depth of 30.5 m).
It was now important to protect the mines against German counter-reactions. This thankless task has been since November 1916 executed by the '1st Australian Tunnelling Company'. German attempts to destroy the charges, could only be avoided at the last minute. The explosion of mines under Hill 60 and Caterpillar, on June 7, 1917, at 3.10am in the morning, was agreed just in time.
Hill 60's crater was 58.2 meters in diameter and 10.1 m deep, the Caterpillar crater was 79.2 m (diameter) and 15.5 m deep. The explosion of the two mines would have killed 687 men in the German 204de Division.