In an article titled Miners of Messines, the Australian reports an account of what happened on June 7, 1917 where a series of 19 underground bombs, totaling 450,000kg of high explosive secretly placed in Allied tunnels under German lines along the Messines ridge in the Ypres area of Belgium and detonated within seconds of each other:
The scene that morning was as if Hades had belched from the earth. The medieval stratagem of laying mines to break into besieged fortresses had reached its zenith. War correspondent Philip Gibbs called it "the most diabolical splendour I have ever seen". An unidentified tunneller writing in 1930 recalled: "All hell broke loose. It was indescribable. In the pale light it appeared as if the whole enemy line had begun to dance. Then, one after the other, huge tongues of flame shot hundreds of feet into the air." Another witness said: "Truly, the earth quaked."
Excellent post! As a former Engineer officer and a history buff, I really enjoyed it. The term “Sappers” came about from the use of mines to undermine castle walls as a technique of siege warfare. The Union Army was successful at breaching the defenses of both Vicksburg and Petersburg with mines, but failed to properly exploit the breaches with adequate infantry support.
I do believe this incident killed 25,000 Germans immediately. Literally thousands of them were killed in their trenches standing up, as the walls of the trenches fell inwards on them and thus, crushing them. Many of the Germans, in the area of the crater, as still there as their final resting place.