Subterranean Thunder: The Seismic Devastation of the Battle of Messines

What happens when an army spends over a year silently digging beneath enemy lines, packing underground chambers with one million pounds of high explosives, and detonating them all at the exact same moment? The Battle of Messines in 1917 unleashed a man-made earthquake so violent it was physically felt by the Prime Minister in London, 130 miles away. To break the brutal stalemate of the Western F...