Chapter 6: Our Premortal Life, C: God the Father provided the plan of salvation by which HIs spirit children could eventually become like Him.

From the beginning God had a plan for us. It is important that we know that God has a plan, and the basics of that plan, because otherwise earth life seems pointless and silly. It is easy to understand how some people ridicule the idea of God when so many Christians belief extends little further than the righteous go to heaven and the wicked go to hell. When we understand WHY that is, and the purpose of this earth life, we are better able to understand and have faith in our Father in Heaven.

For a more structured/detailed description of the plan of salvation please go to mormon.org's explanation of the plan of salvation.

In the beginning God taught us as spirits about the plan. From the beginning, it was Christ who would be our Savior.

And there stood one among them that was like unto God, and he said unto those who were with him: We will go down, for there is space there, and we will take of these materials, and we will make an earth whereon these may dwell; And we will prove them herewith, to see if they will do all things whatsoever the Lord their God shall command them; And they who keep their first estate [premortal life with God the Father in heaven] shall be added upon; and they who keep not their first estate shall not have glory in the same kingdom with those who keep their first estate; and they who keep their second estate shall have glory added upon their heads for ever and ever. And the Lord said: Whom shall I send? And one answered like unto the Son of Man: Here am I send me. And another answered and said: Here am I, send me. And the Lord said: I will send the first.
Abraham 3:24-27

But behold, my Beloved Son, which was my Beloved and Chosen from the beginning, said unto me--Father, they will be done, and the glory be thine forever.
Moses 4:2

But with the precious blood of Christ, as of a lamb without blemish and without spot: Who verily was foreordained before the foundation of the world, but was manifest in these last time for you.
1 Peter 1:19-20

When the great War in Heaven was fought, Lucifer, the son of the morning, came forth with a plan that was rejected. The Father of us all, with love for us, His children, offered a better plan under which we would have freedom to choose the course of our lives. His Firstborn Son, our Elder Brother, was the key to that plan. Man would have his agency, and with that agency would go accountability. Man would walk the ways of the world and sin and stumble. But the Son of God would take upon Himself flesh and offer Himself a sacrifice to atone for the sins of all men. Through unspeakable suffering He would become the great Redeemer, the Savior of all mankind.
Gordon B. Hinckley, Ensign, May 2002, 90

In the premortal life, Satan was an authority figure. When he rebelled against God by trying to take the glory to himself and take away the agency of man, there was a war. This was a war, as far as I can see, not with guns and armies, but for the spirit children of God. Those who fought with Satan eventually were thrust from heaven. This was approximately 1/3 of the spirit children of Heavenly Father.

And I, the Lord God, spake unto Moses, saying: That Satan, whom thou has commanded in the name of mine Only Begotten, is the same which was from the beginning, and he came before me, saying--Behold, here am I, send me, I will be thy son, and I will redeem all mandking, that one soul shall not be lost, and surely I will do it; wherefore give me thine honor. But behold, my Beloved Son, which was my Bheloved and Chosen from the beginning, said unto me--Father, they will be done, and the glory by ehtine forever. Wherefore, because that Satan rebelled against me, and sought to destroy the agency of man, which I, the Lord God, had given him, and also, that I should give unto him mine own power; by the power of mine Only Begotten, I caused that eh should be cast down.
Moses 4:1-3

And this we saw also, and bear record, that an angel of God who was in authority in the presence of God, who rebelled against the Only Begotten Son whom the Father loved and who was in the bosom of the Father, was thrust down from the presence of God and the Son, And was called Perdition, for the heavens wept over him--he was Lucifer, a son of the morning. And we beheld, and lo, he is fallen! is fallen, even a son of the morning! And while we were yet in the SPirit, the Lord commanded us that we should write the vision; for we beheld Satan, that old serpten, even the devil, who rebelled against God, and sought to take the kingdom of our God and his Christ-- Wherefore, he maketh war with saints fo God, and encompasseth them round abouth.
D&C 76:25-26

And there was war in heaven: Michael and his angels fought against the dragon; and the dragon fought and his angels, And prevailed not, neither was their place found any more in heaven. And the great dragon was cast out, that old serptent, called the Devil, and Satan, which deceiveth the whole world: he was cast out into the earth, and his angels were cast out with him.
Revelation 12:7-9

What Satan wanted, quite evidently, was the full possession, ownership, of this creatio of spirits that is involved in the peopleing of this earth; so he tried to get them by gift, and that being denied, he is following along and trying to get us through the comission of sin. If we sin sufficiently we become his subjects.
As I read the scriptures, Satan's plan required two things: Either the compulsion of the mind, the spirit, the intelligence of man, or else saving men in sin. I question whether the intelligence of man can be compelled. Certainly men cannot be saved in sin, because the laws of salvation and exaltation are founded in righeousness, not in sin.
J. Rueben Clark Jr., in Converence Report, Oct. 1949, 13

The scriptures talk about the first estate and second estate. As far as I read, the first estate was our life with Father in heaven and the opportunity to come to the Earth and receive a body. Living with our Father in Heaven was a great privelege as we were able to learn from him and become more like him as we learned, so losing that privelege was a great loss. The loss of the body also meant that they could never progress further. The second estate is what we are concerned with in this life - it is the ability to eternally progress and truly become like our Father in Heaven. That may not be a perfect summation of things as they are, but that is what I understand at this point in time. (See Disclaimer.) Those sould who were with Christ in the war in heaven kept their first estate, while those who were with Satan lost it. In this life we are striving to keep our second estate.

And they who keep their first estate shall be added upon; and they who keep not their first estate shall not have glory in the same kingdom with those who keep their first estate; and they who keep their second estate shall have glory added upon their heads forever and ever.
Abraham 3:26

And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day.
Jude 1:6

The punishment of Satan and the third of the host of heaven who followed him, was that they were denied the privilege of being born into this world and receiving mortal bodies. They did not keep their first estate and were denied the opportunity of eternal progression. The Lord cast them out into the earth, where they became the tempters of mankind-the devil and his angels.
Smith, Doctrines of Salvation, 1:65