18 There were lightnings, sounds, and thunders; and there was a great earthquake, such as was not since there were men on the earth, so great an earthquake, so mighty.
a great earthquake – a great war, see also Rev 11:13 which described the war that killed “a tenth of the City” who died in the Reformation and ongoing religious wars. This “great earthquake” destroys a third of mankind as mentioned in Rev 9:15.