The return of the Lord to the earth is given in glorious terms in the Scriptures. John's writing becomes breathtaking:
And I saw heaven opened, and behold a white horse; and He that sat upon him was called Faithful and True, and in righteousness He doth judge and make war.
His eyes were as a flame of fire, and on His head were many crowns; and He had a name written, that no man knew, but He Himself.
And He was clothed with a vesture dipped in blood; and His name is called The Word of God.
And the armies which were in heaven followed Him upon white horses, clothed in fine linen, white and clean.
And out of His month goeth a sharp sword, that with it He should smite the nations; and He shall rule them with a rod of Iron: and He treadeth the winepress of the fierceness and wrath of Almighty God. And He hath on His vesture and His thigh a name written, KING OF KINGS, AND LORD OF LORDS. (Rev. 19: 11-16)
It is the church that is viewed in verse 14 above. We temporarily come as an army in order to put a stop to the battle of Armageddon, which will be in progress on earth at the moment we return.
Once Armageddon is taken care of, we shall see the judgment of those who lived during the Tribulation Period, and the rewarding of those who refused to receive the mark of the Antichrist, but instead were martyred for their faith in Christ:
And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the Word of God, and which had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years. (Rev. 20:4)
The unbelievers, however, will be bound 1,000 years, until the final judgment:
But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection. (Rev. 20:5)
John exults over the fact that we are blessed to take part in this first resurrection and to reign with Christ through the Kingdom Age:
Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priest of God and of Christ, and shall reign with him a thousand years. (Rev. 20:6)
More details were given by the Lord during His earthly ministry about this judgment, which serves as an immigration office into the Kingdom. He means to take care of every single soul who existed during the seven years on earth, when the Tribulation Period was in progress. The Lord is so perfectly fair. All of the nations will be gathered before Him, and He will separate the believers from the unbelievers "as a shepherd divideth his sheep from the goats":
When the Son of man shall come in His glory, and all the holy angels with Him, then shall He sit upon the throne of His glory: And before Him shall be gathered all nations: and He shall separate them one from another, as a shepherd divideth this sheep from the goats. And He shall set the sheep on His right hand, but the goats on the left.
Then shall the King say unto them on His right hand, Come, ye blessed of my Father, Inherit the kingdom prepared for you from the foundation of the world. (Matt. 25: 31-34)
In reply, the believers will express surprise that they had so honored the Lord during the Tribulation Period, but He will make the matter very clear to them:
And the King shall answer and say unto them, Verily I say unto you, Inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me." (Matt. 25:40)
If the people of the nations of the world, even during the Tribulation Period, demonstrate faith in Christ by caring for his brethren (the 144,000 of Israel who witness during that hard time), they will be saved.
But the judgment is equal and devastating upon those who failed to honor the Lord during the reign of the Antichrist:
Then shall He answer them, saying, Verily I say unto you, Inasmuch as ye did it not to one of the least of these, ye did it not to Me. And these shall go away into everlasting punishment: but the righteous into life eternal. (Matt. 25: 45-46)
The Old Testament saints will be regathered as well at the beginning of the Kingdom Age, and so the kingdom will get under way with rather a mixed crowd, all having in common a sincere belief in the Messiah and King. There will be the faithful of the Old Testament, who waited so long for this grand age, the believers of the Church Age, who went to heaven in the Rapture, and finally the believers of the Tribulation Period, who will enter the Kingdom in their natural bodies. Since they did not come to faith before the Rapture, they were not changed and they remain as they are, still marrying and giving in marriage, unlike the believers of the Church Age. This latter group, the people in their natural bodies, will give birth during the Kingdom to ordinary, fleshly sinners, again "born of Adam." It is these few on earth, in the Kingdom, who will occasionally disobey the Lord's commands and make it necessary for Him to set penalties for failures of worship or sanctity (e.g., Zech. 14:16-19).
These mischief-makers in the Kingdom, having multiplied, will be rallied by Satan in the very last battle at the end of the thousand years:
And when the thousand years are expired, Satan shall be loosed out of his prison. And shall go out to deceive the nations which are in the four quarters of the earth, Gog and Magog, to gather them together to battle: the number of whom is as the sand of the sea. And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them. (Rev. 20: 7-9)
This last rebellion of Satan is unsuccessful and the Great White Throne of Judgment is set up for all those who were confined with him, and the unbelievers of all ages:
And I saw a great white throne, and Him that sat on it, from whose face the earth and the heaven fled away; and there was found no place for them. And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works. And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works. And death and hell were cast into the lake of fire. This is the second death. And whosoever was not found written in the book of life was cast into the lake of fire. (Rev. 20: 11-15)
This second death, then, is that which is avoided by the believers in Christ.