Messines Mine System (Belgium)

The Messines Mine System was a massive network of subterranean tunnels and explosive charges dug beneath the Messines Ridge in West Flanders, Belgium, during World War I. It was constructed by British, Canadian, and Australian tunneling companies to break the German line.

The mines were detonated on June 7, 1917, at the launch of the Battle of Messines. The simultaneous explosions created one of the largest man-made blasts in history up to that point and were reportedly heard as far away as London.

The system consisted of 21 massive underground explosive charges placed along the German front line. Though one mine was delayed and another was lost, 19 of the 21 charges were successfully detonated at the start of the offensive.

The tunnels were constructed in extreme secrecy over the course of two years prior to the 1917 offensive. Thousands of soldiers worked in claustrophobic, waterlogged conditions to dig the shafts and lay the hundreds of thousands of pounds of explosives.