True.
Them alive on earth are changed in a moment, and ascend into the air to meet with the Lord, which is the same as the two witnesses in Rev 11.
I believe the dead in Christ, that are already in the presence of the Lord at His altar in heaven, will receive their resurrected bodies, and be the armies coming with Him out of heaven, to meet with them ascending from the earth.
Since they all come with clouds, I believe that is when the sun and moon are darkened, and the inhabitants remaining on the earth are in darkness over all the earth.
The great tribulation of the saints has been since Cain slew righteous Abel. The last days of our tribulation began with Jesus' resurrection.
Confirming the souls of the disciples, and exhorting them to continue in the faith, and that we must through much tribulation enter into the kingdom of God.
And, behold, as thy life was much set by this day in mine eyes, so let my life be much set by in the eyes of the LORD, and let him deliver me out of all tribulation.
The greatest tribulation any saint has on earth, is the great tribulation of that day.
The end of these last days will be the rise of the last great antichrist beast, and the resurrection of the saints at the Lord's return.
There is the tribulation and wrath of the devil and wicked men upon the righteous, which purifies the faithful, and then there is the tribulation and wrath of God upon all the wicked, that punishes them.
Many shall be purified, and made white, and tried; but the wicked shall do wickedly: and none of the wicked shall understand; but the wise shall understand.
But unto them that are contentious, and do not obey the truth, but obey unrighteousness, indignation and wrath, Tribulation and anguish, upon every soul of man that doeth evil, of the Jew first, and also of the Gentile.
True. That is all the saints of all time since Abel, today, and during Christ's reign, that will stand before God and the Lamb.
I believe that is just prior to New Jerusalem coming down onto the new earth, and just after the final judgment of the Lamb's book of life, because there is no hint nor sense of any of the wicked being anywhere around.
All saints are martyrs in that we must crucify our old man and life of sin. That is why all resurrected saint are said to have been beheaded for the word and testimony of God.
Since Paul plainly speaks of all the dead in Christ, and them remaining alive on earth, will have part in that first resurrection, then being beheaded must be spiritual in nature.
He is said to have been physically beheaded as a Roman, but not all Christians are bodily killed for the faith, though we ought all be willing.
And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell.
Every saint in Christ Jesus must behead the old man from having rule over our life, and welcome the Headship of Jesus over His own body of flesh and bone on earth.
He that findeth his life shall lose it: and he that loseth his life for my sake shall find it.