Revelation 8: 13: And I beheld, and heard an angel flying through the midst of heaven, saying with a loud voice, Woe, woe, woe, to the inhabiters of the earth by reason of the other voices of the trumpet of the three angels, which are yet to sound!
The three woes are connected with the fifth, sixth and seventh trumpets of Revelation 9 and Revelation 11. The fifth trumpet is the first woe, the sixth trumpet is the second woe, and the seventh trumpet is the third woe. The three woes are three world wars to strike the inhabitants of the earth. The first woe was World War One (1914 to 1918), the second woe was World War Two (1939 to 1945), and the third woe is World War Three (Armageddon).