Battle of Messines — 19 Mines Detonated

British forces detonated 19 massive mines—containing 455 tonnes of explosive prepared over 18 months of tunneling—simultaneously under German positions on Messines Ridge. The explosion was heard in London, 210 km away. An estimated 10,000 German soldiers were killed instantly; the ridge was captured within hours. General Plumer's meticulous planning was hailed as a masterpiece, and the battle became a model for subsequent limited objective attacks.