A kingdom is a nation composed of people, as well as the government of that nation. The Kingdom of God is composed of the divine Family of God. The one Being we habitually think of as God is the Father of that family.Christ is a Son of God—a member of that divine Family, even as we may be! That divine Family is the Kingdom of God.

Jesus Christ Himself confirmed that His Kingdom is a literal kingdom: “My kingdom is not of this world: if my kingdom were of this world, then would my servants fight, that I should not be delivered to the Jews: but now is my kingdom not from hence. Pilate therefore said unto him, Art thou a king then? Jesus answered, Thou sayest that I am a king. To this end was I born, and for this cause came I into the world, that I should bear witness unto the truth. Every one that is of the truth heareth my voice” (John 18:36-37).

It wasn’t time for Christ to set up the Kingdom of God yet.

In Just What Do You Mean Born Again?, Mr. Armstrong gave seven points explaining why Christ didn’t immediately start His Kingdom on Earth, even though He had qualified to rule it.

1. God had set a definite plan, with a definite time-program, for working out His purpose here below! It is a 7,000-year plan of seven millennial “days,” of which the first seven literal days of re-creation were a type. The first six of these millennia were allotted for man, of his own free volition (though swayed by Satan) to go his own way. Also, in effect, they were allotted as the six millennial “days” for Satan’s “labor” of deception over humanity, to be followed by the millennial “Sabbath,” in which Satan will observe enforced rest from his work of deceiving the nations, and God will teach humanity His truth!
2. Jesus, in God’s plan, was first to choose and teach disciples to become apostles, to carry on the proclamation of the good news—and to become the foundation of His Church.
3. Christ is going to set up a world government over all Earth’s nations only with the administration of a thoroughly trained and experienced organization. The first 6,000 years of human experience has proved abundantly that man, under Satan’s sway, is utterly incapable of ruling himself. Human-devised governments always have failed to bring world peace. Yet man, even now, seems unwilling to admit that fact. Men are still trying, in vain, to work and fight for peace. And that is where being “born again” comes in. And that, also, is where being “born again” has been tragically misunderstood and misrepresented! God’s government will be divine government, by the saints converted into divine spirit persons, born of God! As those born of humans are human beings, so those born of the divine God will be divine beings, having been given immortality! They shall be born into—enter into—inherit the kingdom of God.
4. In order that man might be reconciled to God, Jesus also came for the express purpose of death, by His shed blood paying for us, in our stead, the death penalty we have incurred as the penalty of sin. In order that we might be given God’s gift of eternal life, Jesus’s resurrection from the dead was necessary before we could receive eternal life.
5. The plan called for Jesus’s ascension to God’s throne in heaven—the throne of the government of God over the universe—to become our High Priest, during these years of training and spiritual development of the heirs of God to be used in the executive administration of the government of God when Christ does set up that government over Earth’s nations.
6. Jesus could not induct Himself into the office while here on Earth in human form. It was necessary for Him, as explained in the parable of the pounds (Luke 19), to go to heaven to there receive the authority of the Kingdom from God (the Father)—and to be crowned! The coronation ceremony will take place in heaven at God’s throne, before Christ’s return in power and glory!
7. Then He must return in all that power and glory and supreme authority to rule!

To read more explaining the Kingdom of God, read the last chapter of Mystery of the Ages.