Revelation 20:4 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.
5 But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection.
6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.
As we continue with the end of Satan’s reign John saw the souls of all those that were martyred for our lord and savior Jesus. They stayed true to their faith in Him and refused to worship or take the mark of the beast. Judgment was given to them immediately and that included living and reigning Christ for 1000 years on this earth. The rest of the dead, the ones killed in the war that were against Jesus, would not be judged until the 1000 year reign is over. When it says this is the first resurrection it means it is a resurrection to life, and on such the second death has no power. Again these in the first resurrection will reign Christ for 1000 years because they are priests of God an Christ. The other dead will be resurrected at the end of the millennial reign just to be judged and face the second death and spend eternity in hell.