The Bible clearly teaches that when Jesus returns to pour out God’s eschatological wrath, the world will be caught off guard and oblivious of his sudden coming.
For example, Jesus uses the Noahic illustration to teach that his return will be sudden upon the world:
For just like the days of Noah were, so the coming of the Son of Man will be. For in those days before the flood, people were eating and drinking, marrying and giving in marriage, until the day Noah entered the ark. And they knew nothing until the flood came and took them all away. It will be the same at the coming of the Son of Man. Then there will be two men in the field; one will be taken and one left. There will be two women grinding grain with a mill; one will be taken and one left. (Matt 24:37–41)
For you know quite well that the day of the Lord will come in the same way as a thief in the night. Now when they are saying, “There is peace and security,” then sudden destruction comes on them, like labor pains on a pregnant woman, and they will surely not escape. (1 Thess 5:1–3)
Jesus and Paul’s teaching contradicts posttribulationism.
Many posttribulationists, on the other hand, believe that after God has pounded the wicked during the trumpet judgments (Rev 8–9), only then will Jesus return at the seventh trumpet.
No sound and sober interpreter can correctly think that Jesus’s return will be “like a thief,” and “as in the days or Noah,” and “as sudden birth pangs” if it occurs after he decimates the world with the wrath of his trumpet judgments. The sixth trumpet by itself says a third of humanity perishes! (Rev 9:18).
And for that reason alone, posttribulationism contradicts the clear teaching of Scripture.
The passages quoted above are also consistent with what we see in the book of Revelation, where the trumpet judgments follow after the opening of the seventh seal (Rev 8:1–6!). Placing the trumpet judgments before the opening of the seventh seal is another contradiction on several levels, especially contradicting Rev 8:1–6.