The Tribulation is not the general time between His first and second comings where believers will have the promised trials and persecutions. The Tribulation is a distinct time referenced as THE Tribulation. It will exist for a set purpose, certain things will happen in an progressive fashion (as prophesied in Revelation 6-18 and elsewhere) and it will cease at its end to usher in a 1000 year kingdom on earth of peace where Jesus walks and reigns with His people. (Revelation 20:2-7, 2 Thessalonians 1:7-8, Daniel 9:24-27, Matthew 24:3-28...)
During this Tribulation, it will be a hell on earth, literally. The abyss is opened and many chained up demons are let out to wreak havoc. (Revelation 9:1-12). It's a time when God's 4 sorest judgments will occur. He releases 4 horsemen to have their fill of death and chaos and sin and evil wrought upon the people. It will be a time of punishment, vengeance, retribution, and wrath. Many millions upon billions die. (Revelation 6:8, Revelation 9:15).
Before I get to my main point, let's turn aside for a comment. People incorrectly view the God of the Bible as a split personality. There's the God of the Old Testament who is wrathful, and the Jesus of the New Testament who is nice. Jesus "hung out with sinners" and spoke the Beatitudes, after all.
God is God and He changeth not. In the OT He rendered wrath, but He was also compassionate and kind. I can give many examples. He spoke gently to Hagar in the wilderness. He sent angels to feed and comfort Elijah. He answered Habakkuk's complaints gently. He gave Hannah the son she prayed for. he spoke to Moses as a friend. And so on.
In the NT, God is kind but He is also wrath. Wrath is mentioned many times in the NT. It's mentioned in Matthew, Luke, John, Romans, Ephesians, Colossians, 1 Thessalonians, Hebrews, and most of all, 11 times in Revelation, where Jesus is rendering it or ordering His angels to deliver it. If you read the Jesus of Revelation, there exists no sissified, needy Jesus at all. He never existed. THAT Jesus is a figment of man's imagination.
Now to the point, despite the horrors of The Tribulation, despite the wrath and death and chaos and sin, God still seeks souls. He saves. He saves many, multitudes one cannot number! They are saved from every language and nation and tribe and tongue! His grace abounds even in wrath.
By what process does He save?
1. His Two Prophets. Their story is contained in a Revelation 11:3-13. Their ministry begins:
And I will grant authority to my two witnesses, and they will prophesy for 1,260 days, clothed in sackcloth.
They preach in Jerusalem and according to prophecy, it's for a set number of days. People will try to kill them. Those who hate the LORD will hate their message of sin and wrath and judgment. But while they are prophesying God's word on earth during the allotted number of days, nothing can harm them. As a matter of fact, they can spew fire and kill those who try to kill them. (Revelation 11:5). When the allotted number of days is up, they will be successfully killed. (Revelation 11:7). Their bodies will lie in the street for three days, and the world rejoices that their devastating message will have been silenced, or so the world thinks. They are resurrected and ascend to heaven before the world's astonished face. (Revelation 11:11-12).
The result is that for 1,260 days the world hears two indestructible witnesses preach the everlasting gospel to the world, whether they want it or not.
The 144,000.
Their story is contained in Revelation 7:3-8 and Revelation 14:1-5. God plucks 12,000 from each Jewish Tribe as His firstfruits of Gospel salvation in their Messiah. Though none of the verses explicitly say that the men from the 144,000 evangelize, it's highly likely that they are agents of the Gospel. The fact that they are chosen, sealed from harm during the judgments indicates that they have work to do. One's relief and joy in Christ always yields a loosened tongue to proclaim His glories. How much more so in the Wrath? Also, the very next scene after they are saved and sealed, we see multitudes of redeemed from the earth. Imagine 144,000 Apostle Pauls running around, lol. People are going to be saved.
The Three Angels at Midheaven.
Their story is in Revelation 14:6-11, but the first angel in verses 6-7 is the one who proclaims the eternal Gospel to the entire world, every nation, tongue, tribe, and people. Every. One. Hears.
What a God we serve! He pursues even as He concludes the last moments of His Age.