Allow me to check as we go along. Some may find it helpful.
"And I heard a loud voice in heaven, saying, Now has come the salvation and the power and the kingdom of our God and the authority of His Christ, for the accuser of our brothers has been cast down, who accuses them before our God day and night." (Rev. 12:10)
Here we are in the 12th chapter of Revelation. Much has gone before. Chronoligically already we have seen God bring the kingdoms of the world all into the kingdom of God and His Christ in chapter 11. So why does this seeming anti-climax of the announcement of Rev. 12:10 come after this:
"And the seventh angel trumpeted; and there were loud voices in heaven, saying, The kingdom of the world has become the kingdom of our Lord and of His Christ, and He will reign forever and ever." (Rev. 11:15)
Part of the answer is that Revelation is divided into two parts. Up to chapter 11 the seventh trumpet concludes the first part. Then chapters 12 REVISIT some of what has already been revealed with a greater focus on the last three and one half years.
The other reason I would submit is that the kingdom announcement of Revelation 11:15 is more outward and objective in nature. In the second section the kingdom matters are more INWARD and SUBJECTIVE. The kingdom must come within the subjective hearts and souls of the overcoming believers before the outward and objective political kingdom comes to the earth.
So we have something more related to the INWARD kingdom of the overcomers which preceeds the OUTWARD coming of His kingdom to rule the world. - "Now has come the salvation and the power and the kingdom of our God and the authority of His Christ . . ."
NOW we have a scene of some (a critical mass) of believers who are not just forgiven. But Christ has subjectively spread His nature into their whole beings. This is the "salvation" in full. This is the "power" in full - the power of the Christ saturated, Christ permeated, Christ mingled humanity which is beyond blame.
The purpose of His salvation was not merely to have forgiven men but transformed men. That is transformed into His own image - the image of the Firstborn Son of God. Through the centuries here and there God did gain some to reach maturity. The gospel continued to be spread throughout the world. Not many believers died in maturity. Many more died in immaturity THOUGH forgiven, redeemed, and gifted with eternal life.
Little did we know there was accumulating in Paradise under the earth not only a QUANTITY of saints but the QUALITY of a remnant, a minority, who had reached maturity. This are the STRONGER component withint the total Universal Body of God's saints. That is why we see a Woman with a Manchild within her. That is a weaker vessel yet containing a stronger component to secure victoty in spiritual warfare.
We first get a glimpse of this remnant of stronger overcomers in the Fifth Seal. That is the marytred saints underneath the altar.
"And when He opened the fifth seal, I saw underneath the altar the souls of those who had been slain because of the word of God and because of the testimony which they had. And they cried with a loud voice, saying, How long, O Master, holy and true, will You not judge and avenge our blood on those who dwell on the earth? And to each of them was given a white robe; and it was said to them that they should rest yet a little while, until also the number of their fellow slaves and their brothers who were about to be killed, even as they were, is completed." (Rev. 6:9-11)
These who are deceased are told to be patient. They are shown approval by the white robes they are given while they are told to wait a little longer for their vindication.
These ones are also the Manchild resurrected and raptured to the third heaven at the appropriate time. For in them the full salvation and power and kingdom of God have come subjectly. You should think of a remnant like army such as Gideon's 300. Their victory is for the benefit of the whole nation. They were the stronger part of the weaker whole nation of Israel. That is weak in terms of being able to fight the warfare for Gods's
interests on earth.
This is true in a sense. But many died being overcome by the opposition. Like the souls underneath the altar in the Fifth Seal they were to rest until their number is filled up. And they were to rest quite approved yet to be patient for their total vindication.
Though the kingdom of God was initiated in the first century the climax of its accomplishment is not with their martyrdom but with their resurrection, vindication, and rapture to the throne of God about three and one half years before the consummation of the age.
The number of their fellow martyrs is completed (by God's will). And from the majority of believers they have a pre-great tribulation resurrection and rapture. Following thier rapture there is no more room in the heavens for Satan to accuse. They give the command for Satan to be expelled from that realm.
As if to say "Satan, what are you doing here? We have arrived now and you have to get out. We overcame you on the earth even though you had us killed. But we have now been resurrected and raptured as glorified sons of God and we overcome you now even in the heavens."
Actually we should preach to Satan this way anyway. Even as you rightly taught that Christ has nullified his accusation. So even in the church while we await the coming of Christ with myriads of His victorious saints (Jude 14). We need not wait to preach to Satan his total defeat.
So though the opening of the doors of the church was the opening of the kingdom of the heavens to men, its culmination was not at that time practically. John in exile on the island of Patmos was a active worker FOR the kingdom with endurance and patience.
Revelation 1:9 - "I John, your brother and fellow partaker in the tribulation and kingdom and endurance in Jesus, was on the island called Patmos because of the word of God and the testimony of Jesus."
So I dare not say the kingdom of God had not come in the first century. But we also must see that the kingdom is in stages from inception, through growth, through maturity, through ripeness and climax - the harvest.
Mark 4:26-29 -
"And He said, So is the kingdom of God: as if a man cast seed on the earth,
And sleeps and rises night and day, and the seed sprouts and lengthens — how, he does not know.
The earth bears fruit by itself: first a blade, then an ear, then full grain in the ear.
But when the fruit is ripe, immediately he sends forth the sickle, because the harvest has come."
You see? At each STAGE along the process of growth you still have the kingdom of God.
So the kingdom was at an early stage in the first century.
There is the need for growth, spread, maturity, and finally full ripening harvest.
Each stage is a stage of the kingdom.
The three disciples were given a preview of the kingdom. Christ was a man with the glory of God concealed in the flesh of His humanity.
The shekeniah glory of the divine life was concealed within Him for His whole earthly life.
On this occasion He gave three of His closest disciples a glimpse of this glorified humanity. In a sensee He "unzipped" Himself to reveal the divine glory hidden before within Him. This He showed them as a PREVIEW of the coming age in which not only He but also they too would participate in this MANFESTATION of the divine life dispensed into man.
This was His showing us the kingdom's coming. This was Him revealing a foretaste, preview, and glimpse into the powers of the age to come (Heb 6:5)
At the time shortly before the close of this age, some living and some deceased overcoming saints will be raptured or resurrected and raptured into this situation. That is saturated from within and manifested without the divine glory just like Christ.
For our commonwealth exists in the heavens, from which also we eagerly await a Savior, the Lord Jesus Christ,
Who will transfigure the body of our humiliation to be conformed to the body of His glory, according to His operation by which He is able even to subject all things to Himself. (Phil. 3:20,21)
I see your answer as partially right.
I tried to show you that we have now and presently "An Advocate with the Father, Jesus Christ the Righteous."
Someone is accusing us now. And it is not the Father. So it must be the accuser of the brothers - Satan.
I have tried to show you that the first century saints left their testimony during that stage of the development of the kingdom (Mark 4:26-29).
Though the sprouting is a stage of the kingdom there is a process culminating in harvest which is also all the kingdom of God too.
So by saying "Now has come the salvation and the power and the kingdom of our God and the authority of His Christ"
This should not be taken as saying there was no kingdom of God in the first century nor salvation nor authority of Christ then.
To repeat: To say the resurrection and rapture of the overcomers approximately 1,260 days before the close of the age prompts the voice to say "Now has come the salvation and the power and the kingdom of our God and the authority of His Christ" is in no way to deny the presence of God's salvation, kingdom, authority from the first century. God forbid.
It is a matter of ripeness having been acheived.
It is a matter of harvest of a mature critical mass having been at long last vindicated.
Thier rapture MEANS the descent of Satan from his tolerated position of accusation through the church age.
They have been raptured beyond blame for their daily lives. Any errors they made were advocated for by the Advocate who shed His blood for them. They overcame by the Lamb's blood. They overcaome by standing on the FACTS and proclaiming the truths of the God's promises. Against sight they walked by faith (as we all should).
And particularly these of the Manchild died for their faith because it says loved not thier soul-life even UNTO DEATH.
" And they overcame him because of the blood of the Lamb and because of the word of their testimony, and they loved not their soul-life even unto death."
Now it would be a mistake to misunderstand me to be saying we need to WAIT before we Christians live this way.
No indeed. This should be a model of what would be the normal Christian life.
Whether we are martyred or not is up to God's sovereignty. But all believers should not love the self over the Lord.
And all believers should learn the power of the blood of Christ to shut the accuser's mouth. And all beleivers should learn to
stand on the FACTS of God's precious promises as "the word of their testimony."
In the meantime, the rapture of these overcomers, this Manchild to heaven, necessarily means Satan is then driven down at last to being limited to the earth. This enrages him. And as a result of knowing he has only a short time left, unleashes all his final efforts during the last three and a half years of the age.
Those raptured to the throne in heaven are GLAD and REJOICING. But those Christians and elect Jews upon the earth still are warned of the impending short time of the Devil's intense anger agaisnt God's elect who are to follow.
"Therefore be glad, O heavens and those who dwell in them. Woe to the earth and the sea because the devil has come down to you and has great rage, knowing that he has only a short time. And when the dragon saw that he was cast to the earth, he persecuted the woman who brought forth the man-child." (Rev. 12:12,13)