The Gospels show that this tribulation will not start and end at one fell swoop. After it begins, some of disobedient mankind will still be alive to see “the sign of the Son of man” and to react​—to lament and, as stated at Luke 21:26, to “become faint out of fear and expectation of the things coming upon the inhabited earth.” That overwhelming fear will be due to their seeing “the sign” that betokens their imminent destruction.

21. How will a future “sign” occur?

²¹ At this point all three Gospel writers use toʹte (then) to introduce the next development. “Then the sign of the Son of man will appear in heaven.” (Matthew 24:30; Mark 13:26; Luke 21:27) Since World War I, Jesus’ true disciples have discerned the composite sign of his invisible presence, while most people have not recognized it. But Matthew 24:30 points forward to a further “sign” appearing in the future, that of “the Son of man,” and all nations will be compelled to take note. When Jesus comes with clouds of invisibility, opposing humans worldwide will have to recognize that “coming” (Greek, er·khoʹme·non) because of a supernatural demonstration of his kingly power.​—Revelation 1:7.