Sappers and miners at work, Ypres salient, Belgium, World War I, c1915-c1917. Artist: Realistic Travels Publishers

Sappers and miners at work, Ypres salient, Belgium, World War I, c1915-c1917. Digging a tunnel under Hill 60. Hill 60 was a strategically important high point on the southern edge of the Ypres salient that had been captured by the Germans in 1914 as they advanced towards the sea. The Germans were dislodged from the hill in April 1915 after British engineers detonated exposives placed in tunnels dug into the hill, but recaptured it following a gas attack the following month. Australian troops took over mining operations at Hill 60 in November 1916 and on 7 June 1917, at the beginning of the Battle of Messines, they set off 450,000 kg of explosives in 19 tunnels. A large part of the hill was destroyed and 10,000 Germans killed in their trenches in an explosion that was said to have been heard and felt as far away as London and even Dublin. Stereoscopic card. Detail. (Photo by The Print Collector/Print Collector/Getty Images)