It should not be missed that in accordance with Gods desire that all should come to repentance (2Pe. 2Pe. 3:9), the events of the book of Revelation are intended to serve as a final call to those who God knows will yet respond to the message of the gospel. This can be seen in the special ministries of the 144,000 Jewish servants (Rev. Rev. 7:1+, Rev. 14:1+), the two witnesses (Rev. Rev. 11:3+), and the angel proclaiming the gospel message worldwide (Rev. Rev. 14:16+). In response to their testimony, a large number of people will come to faith in Christ, although many will be martyred (Rev. Rev. 6:9-11+; Rev. 7:13-14+).1
Those who refuse to respond to the gospel message are shown to be unbending in their rejection of God and without any hint of repentance (Rev. Rev. 9:20-21+; Rev. 16:9+, Rev. 16:11+, Rev. 16:21+). Thus, the events preceding the Second Coming of Christ serve as a global threshing where the wheat (believers) is separated from the chaff (unbelievers) by the extreme tests which come upon the world (Luke Luke 21:34-36; Rev. Rev. 3:10+). In our sorrow over the destiny of the chaff, let us not overlook the wheat which is harvested to the glory of God (Rev. Rev. 14:14-16+).
1 By means of the 144,000 Jews, God will accomplish the second purpose of the Great Tribulation, that of bringing about a worldwide revival.Arnold G. Fruchtenbaum, The Footsteps of Messiah, rev ed. (Tustin, CA: Ariel Ministries, 2003), 179-180.