In Revelation 18 an Angel gives the 'Loud Cry' and Babylon is described in detail and the call made to come out of her, and the warning given that "God hath remembered her iniquities."

Revelation 18:1-5
1 And after these things I saw another angel come down from heaven, having great power; and the earth was lightened with his glory.
2 And he cried mightily with a strong voice, saying, Babylon the great is fallen, is fallen, and is become the habitation of devils, and the hold of every foul spirit, and a cage of every unclean and hateful bird.
3 For all nations have drunk of the wine of the wrath of her fornication, and the kings of the earth have committed fornication with her, and the merchants of the earth are waxed rich through the abundance of her delicacies.
4 And I heard another voice from heaven, saying, Come out of her, my people, that ye be not partakers of her sins, and that ye receive not of her plagues.
5 For her sins have reached unto heaven, and God hath remembered her iniquities.

We see the angel cry "mightily with a strong voice", and "the earth was lightened with his glory." Here is pictured the final announcement of the fall and demon possession of Babylon, accompanied by the divine call, "Come out of her, My people." The separation from Babylon is necessary in order to be emancipated from her sins and to escape her plagues.

The time of the loud cry is definitely located. It comes just before the close of probation and the falling of the seven last plagues, in which "is filled up the wrath of God." With a loud c ry or strong voice the call is given for God's people remaining in the religious organizations constituting Babylon to separate from what has "become the habitation of devils, and the hold of every foul spirit, and the cage of every unclean and hateful bird." Babylon includes the mother and the large family of daughters, all of whom have fallen and been taken possession of by Satanic agencies.

The loud cry is the final message of salvation during the outpouring of the Holy Spirit as prophesized in the last days, a call which will bring every human being to a final and irrevocable decision. The latter rain furnishes the power so that the message can be quickly finished and bring any of Gods people out of Babylon.

It is evident that the purpose of the loud cry is to call out of Babylon all who had not previously made the separation. This must be done before probation closes and the plagues fall. The Lord designates those called out as "My people" to escape from Babylon, a doomed spiritual entity which is followed in wonder by the world.

Why the great urgency to come out and separate from it, because Babylon has become completely possessed and controlled by satanic forces, has fallen to an all-time low level of spiritual life, and is clearly a unfitting dwelling place for the people of God. The sins of Babylon, like the tower of Babel in ancient Babylon, have piled up until they have "reached unto heaven, and God hath remembered their iniquities." Just as the angels hurried Lot and his family out of the doomed city of Sodom before its destruction, so the saints of God must be hastened out of the final spiritual city of destruction before the wrath divine brings it to a deserved end.

When Peter wrote his first epistle, he concluded by saying, "The church that is in Babylon, elected together with you, saluteth you" (1 Peter 5:13, KJV). In the Roman Catholic Douay Version of the Bible, the footnote to this verse says, 'Babylon. Figuratively Rome.' During the Protestant Reformation all leaders taught essentially the same, from Luther, in 1520, onward. These men were scattered over Germany, Switzerland, France, and England. In Britain were men like William Tyndale, Bishops Ridley and Hooper, Archbishop Cranmer, Bishops Bale, Jewell, and Coverdale, and John Knox and others. Bishops Ridley's farewell letter before his martyrdom, in 1555, repeatedly referred to "Babylon," and called for separation from Rome. We see the rise of the woman on the scarlet-colored beast which is Babylon, clearly the Papacy, the doomed spiritual entity that Gods people must come out of.

When Pagan Rome fell, the rise of Papal Rome was more of a transition into a religious-political government and is the woman riding a scarlet-colored beast, and prophecy tells us the Roman Catholic Church moves on until end with the kings of the earth committing fornication with her, but her doom is coming.

Today we see the kings and leaders, and the world, looking more and more to the Pope for guidance in national and religious affairs. It is this mixing of the two that allows the advance the church's authority and develops the fornication of the kings or world powers with the church.

The system with political and monetary side has not fallen although the religious and spiritual side is dead or dying for the most part, you can see it in the empty Cathedrals and Catholic churches. But the daughter churches also are going to suffer as they continue its practices and joining its call for ecumenism to unite the world under its lead and its goal of a united world religion under head, the Pope, which we see them slowly drifting towards.

We see the complete sequence given in Revelation 14...
Revelation 14:6-11
6 And I saw another angel fly in the midst of heaven, having the everlasting gospel to preach unto them that dwell on the earth, and to every nation, and kindred, and tongue, and people,
7 Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and worship him that made heaven, and earth, and the sea, and the fountains of waters.
8 And there followed another angel, saying, Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication.
9 And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand,
10 The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb:
11 And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who worship the beast and his image, and whosoever receiveth the mark of his name.

So what is the prophecy about, well here is a good description on it..
'In the eighteenth chapter of the Revelation the people of God are called upon to come out of Babylon. According to this scripture, many of God's people must still be in Babylon. And in what religious bodies are the greater part of the followers of Christ now to
be found? Without doubt, in the various churches professing the Protestant faith.--GC 383 (1911).

Notwithstanding the spiritual darkness and alienation from God that exist in the churches which constitute Babylon, the great body of Christ's true followers are still to be found in their communion.--GC 390 (1911).

Babylon's Fall Not Yet Complete​
"She made all nations drink of the wine of the wrath of her fornication" (Rev. 14:6-8). How is this done? By forcing men to accept a spurious sabbath.--8T 94 (1904).

Not yet, however, can it be said that . . . "she made all nations drink of the wine of the wrath of her fornication." She has not yet made all nations do this. . . . Not until this condition shall be reached, and the union of the church with the world shall be fully accomplished throughout Christendom, will the fall of Babylon be complete. The change is a progressive one, and the perfect fulfilment of Revelation 14:8 is yet future.--GC 389, 390 (1911).

When do her sins reach unto heaven [Rev. 18:2-5]? When the law of God is finally made void by legislation.--ST June 12, 1893.

God's Last Warning Message​
God has given the messages of Revelation 14 their place in the line of prophecy and their work is not to cease
till the close of this earth's history.--EGW'88 804 (1890).

Revelation 18 points to the time when, as the result of rejecting the threefold warning of Revelation 14:6-12, the church will have fully reached the condition foretold by the second angel, and the people of God still in Babylon will be called upon to separate from her communion. This message is the last that will ever be given to the world.--GC 390 (1911).

[Rev. 18:1, 2, 4, quoted.] This scripture points forward to a time when the announcement of the fall of Babylon, as made by the second angel of Revelation 14 (verse 8), is to be repeated, with the additional mention of the corruptions which have been entering the various organisations that constitute Babylon, since that message was first given, in the summer of 1844. . . . These announcements, uniting with the third angel's message, constitute the final warning to be given to the inhabitants of the earth. . . .

The sins of Babylon will be laid open. The fearful results of enforcing the observances of the church by civil authority, the inroads of spiritualism, the stealthy but rapid progress of the papal power--all will be unmasked. By these solemn warnings the people will be stirred. Thousands upon thousands will listen who have never heard words like these.--GC 603, 604, 606 (1911).

So what does it point to, its clear its a religious-political power, a image of the original and we see it forming today, and SOP gives even more on it...

'But today in the religious world there are multitudes who, as they believe, are working for the establishment of the kingdom of Christ as an earthly and temporal dominion. They desire to make our Lord the ruler of the kingdoms of this world, the ruler in its courts and camps, its legislative halls, its palaces and market places. They expect Him to rule through legal enactments, enforced by human authority.

Since Christ is not now here in person, they themselves will undertake to act in His stead, to execute the laws of His kingdom. The
establishment of such a kingdom is what the Jews desired in the days of Christ. They would have received Jesus, had He been willing to establish a temporal dominion, to enforce what they regarded as the laws of God, and to make them the expositors of His will and the agents of His authority. But He said, "My kingdom is not of this world." John 18:36. He would not accept the earthly throne. {DA 509.2}

Protestant churches that have followed in the steps of Rome by forming alliance with worldly powers have manifested a similar desire to restrict liberty of conscience. In the seventeenth century thousands of non-conformist ministers suffered under the rule of the Church of England. Persecution always follows religious favoritism on the part of secular governments. {4SP 277.2} Rev.
18:3,9-24.

The Protestant churches, having received doctrines that the Word of God condemns, will bring these to the front and force them upon the consciences of the people, just as the papal authorities urged their dogmas upon the advocates of truth in Luther?s time. The same battle is again to be fought, and every soul will be called upon to decide upon which side of the controversy he or she will be found. {CTr 323.5}

"Babylon has been fostering poisonous doctrines, the wine of error. This wine of error is made up of false doctrines, such as the natural immortality of the soul, the eternal torment of the wicked, the denial of the pre-existence of Christ prior to His birth in Bethlehem, and advocating and exalting the first day of the week above God's holy and sanctified day. These and kindred errors..." TM 61.3. also GC 389, 586.

The great city is divided into three parts; that is, the three grand divisions of the false and apostate religions of the world (the great city),
Paganism, Catholicism, and relapsed Protestantism, seem to be set apart each to receive its appropriate doom. The cities of the nations fall; universal desolation spreads over the earth; every island flees away, and the mountains are not found; and great Babylon comes in remembrance before God. Read her judgments, as more fully described in chapter 18. {1897 UrS, DAR 653.4}

Very true -- In Revelation 18 an Angel gives the 'Loud Cry' and Babylon is described in detail and the call made to come out of her.

But let's look at the other side of this equation.
It's not enough to disfellowship ourselves from Babylon. Babylon is darkness, yes people need to leave that darkness, but this angel brightens the earth with GLORY.
What is the GLORY? the most important part of this call?

dedication,

I think your question can be answered by a better understanding of what happens at the latter rain, during which time the loud cry happens. Ellen White had this to say:

At the loud cry of the angel from heaven who joins the third angel, thousands will awake from the stupor that has held the world for ages, and will see the beauty and value of the truth" The Review and Herald December 15, 1885, Art. A paragraph 15 (Ellen G. White, https://egwwritings.org/?ref=en_RH.December.15.1885.Art.A.par.15&para=821.6914)

At that time the ?latter rain,? or refreshing from the presence of the Lord, will come, to give power to the loud voice of the third angel, and prepare the saints to stand in the period when the seven last plagues shall be poured out.?Early Writings, 86 (1854). {LDE 186.4, https://legacy.egwwritings.org/?ref=en_LDE.186.4&para=39.1194 }

I have no specific time of which to speak when the outpouring of the Holy Spirit will take place?when the mighty angel will come down from heaven and unite with the third angel in closing up the work for this world. My message is that our only safety is in being ready for the heavenly refreshing, having our lamps trimmed and burning.?{Selected Messages 1:192 (1892), https://legacy.egwwritings.org/?ref=en_1SM.192.1&para=98.1178,

So, to summarize what she says, The fourth angel, the angel from Rev. 18:1-3, when it comes, it will unite with the third angel's message and will cause the loud cry. Further, the Holy Spirit will come with it to give the combined message great power.

Now, in regard to the glory, she says this:

At the transfiguration, Jesus was glorified by his Father. From his lips came these words: ?Now is the Son of man glorified, and God is glorified in him.? Before his betrayal and crucifixion he was strengthened for his last dreadful sufferings. As the members of Christ's body approach the period of their final conflict they will grow up into him, and will possess symmetrical characters. As the message of the third angel swells to a loud cry, great power and glory will attend the closing work. It is the latter rain, which revives and strengthens the people of God to pass through the time of Jacob's trouble referred to by the prophets. The glory of that light which attends the third angel will be reflected upon them. God will preserve his people through that time of peril. (ST November 27, 1879, par. 10, https://egwwritings.org/read?panels=p820.1956&index=0, underlining by author)

She also says this:

Several have written to me, inquiring if the message of justification by faith is the third angel's message, and I have answered, " it is the third angel's message in verity." The prophet declares, "And after these things I saw another angel come down from heaven, having great power; and the earth was lightened with his glory." Brightness, glory, and power are to be connected with the third angel's message, and con-
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viction will follow wherever it is preached in demonstration of the Spirit. How will any of our brethren know when this light shall come to the people of God? As yet, we certainly have not seen the light that answers to this description. God has light for his people, and all who will accept it will see the sinfulness of remaining in a lukewarm condition ; they will heed the counsel of the True Witness when he says, "Be zealous therefore, and repent. Behold, I stand at the door, and knock : if any man hear my voice, and open the door, I will come in to him, and will sup with him, and he with me."

Now, she says they had not seen the brightness, glory and power that comes with the fourth angel (the one that is yet to come down from heaven). Why did she say this? They had Revelation 18 right in front of them, so how could they miss it? Why was not the power, glory and brightness there with them? I know that the reason is because they did not understand it as much as they thought they did. When it is properly understood, and the things it predicts happen, then the power, brightness and glory will come and attend it - and not before. Revelation 18 is summarized in Rev. 1716-17 and to have the power, glory and brightness, Rev. 17 must be correctly understood and then Rev. 18's warning embedded within it and taught. Then that power, brightness and glory will come.

It is very important to grasp the message of righteousness by faith in the third angel's message, as well as in the fourth (in Rev. 18) which is actually a swelling into a loud cry of the previous three. Good quotes you shared, Wendell.

It's not just what denomination one is a member in (though finding the right church is important as is escaping error and settling into truth). Most important however, is: " who is our Master" Who do we belong to? Who has our heart felt devotion and worship? It is only those who have given themselves fully to Christ, who will receive the Holy Spirit and be able to shine forth, not in their glory, but in God's glory.

Without that, all the adherence to law and knowing doctrine is just surface attachments that fall short of the glory God is offering to all who fully surrender, follow and worship Him.

There are many connections between the third angel's message and the message of Christ our righteousness that a surface reading of the passage can easily miss.

Babylon is fallen. What does that mean?
If we go back in history to Babylon's very beginning, we find a people building a tower to save themselves. They didn't believe God's covenant promise in Genesis 9:11 And I will establish my covenant with you; all flesh shall never again be cut off by the waters of a flood; neither shall there any more be a flood to destroy the earth. They figured they had to save themselves.
That's the foundation upon which Babylon stands. Finding a supposedly better way to ensure salvation rather than God's way.

The third angel's message sees those keeping God's commandments as the "saints" and blessed ones. (Rev. 14:17) But according to Daniel 7:25 a power that thinks it can change times and laws holds considerable influence and power. Rev. 13 shows almost the whole world gives their homage to that power instead of to Christ.

Ellen White writes that


So we see two aspects to all of this --
1. Only in Christ can we have the "righteousness of Christ". We can't do it in our strength, we can't offer Him our own works as merits for salvation, without Him we perish. It is His mercy and grace working for us and in us.
2. That righteousness, the righteousness of Christ, will be revealed in obedience to God's will and law, from a new heart by the power of the Holy Spirit, fully trusting and surrendered to Christ.

Thus any system or spiritual rituals and practices that works outside, or against these conditions is Babylon, placing their own opinions, and practices above God's will, law, grace and mercy.

A system that offers "merits" coming from deceased "saints" who supposedly have stored up "extra" merits: Or the whole idea of "paying for our sins" by penance or in purgatory, or some ritual, etc. is Babylon.

Even Sabbath keeping -- the outward actions don't give us merits for salvation. If the heart isn't with Christ no amount of stopping from work and going to church grants salvation.
Rather
The Sabbath is resting in Christ's merits and worshipping Him as our Savior and Lord and Redeemer. It's not works, it's about acknowledging Him as our Savior, Creator, and resting and rejoice in Him. A little foretaste of being in heaven with Him. As He sanctified the 7th day making it holy, a blessed sanctuary in time, so those who remember the true sabbath remember it is He that not only created them but also sanctifies them and makes them holy. (See Ez 20:12,20)

Sunday --
Man says, sorry I'll keep a day of my own choosing that's more convenient, and popular, not God's day. Like Cain bringing an alternate offering to God.

Rev. 14:7 worship him that made heaven, and earth, and the sea, and the fountains of waters.
Ex. 20:11 For in six days the LORD made heaven and earth, the sea, and all that is in them , and rested the seventh day: wherefore the LORD blessed the sabbath day, and sanctified it. (made it holy)
Ez. 20:12 I gave them my sabbaths, to be a sign between me and them, that they might know that I, the LORD that sanctify them.
Rev.14:4 These are they which follow the Lamb whithersoever he goes. These were redeemed from among men,

Here is from my notes for my sermon,,,
Lets turn now to James 5:7 which tells us something important on this:

James 5:7
Be patient therefore, brethren, unto the coming of the Lord. Behold, the husbandman waiteth for the precious fruit of the earth, and hath long patience for it, until he receive the early and latter rain.

You see what it says, it puts together the 'latter rain' and the 'early rain' that is poured out as we wait. Now its important to understand that we need to experience the early rain to awaken us and spiritually grow to be prepared for the latter rain which prepares Christians for the final crisis and Christ?s return. And this is where we are today, and there is no reason to hold back and not ask now for the Holy Spirit even in its early rain stage for us, because there are some in the church that wrongly feel that they must wait for the latter rain of the Spirit in order to change spiritually and truly overcome. Is that what we should do, as Paul says, 'God forbid', we have the signs of the time showing up daily. If we hesitate and hold back now, it can take you down a wrong path if allowed, as the early rain of the Spirit, brings us to the level we need to be at, in order to receive and grow from the latter rain.

We see more on this from SOP:
?The latter rain, ripening earth?s harvest, represents the spiritual grace that prepares the church for the coming of the Son of man. But unless the former rain has fallen, there will be no life; the green blade will not spring up. Unless the early showers have done their work, the latter rain can bring no seed to perfection? (The Faith I Live By, p. 333).

Those who do not heed it, will be like those on the day of Pentecost who did not receive the initial outpouring of the early rain, and wondered what it is. They will not understand what is happening and will be confused or even try to hold back those who are experiencing the fullness of God?s power at the outpouring of the Holy Spirit. They have not prepared, and we dont want to be in this state at the end, we want to be ready, so there is work to be done now. We cant come on Sabbath and just warm the seat and say I will just wait for the signs, to what we know will be the time such as never was, where the image to Beast will rise up and more, and then decided to ask for the outpouring. We cannot wait but ask for the Holy Spirit with much prayer, allow its power, and we put on the whole armor of God, for the time such as never was of the end.
Lets look at Ephesians 6:13-18:

Ephesians 6:13-18
13 Wherefore take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand.
14 Stand therefore, having your loins girt about with truth, and having on the breastplate of righteousness;
15 And your feet shod with the preparation of the gospel of peace;
16 Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the wicked.
17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God:
18 Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints;

Notice how it says to pray, "with all prayer and supplication in the Spirit". We put on the whole armor and as the Holy Spirit is imparted, it gives strength to not only the proclamation of the Gospel but what is the loud cry of the third angel and its message. The effect of the loud cry on the world will cause a reaction, and much as the High Priest and religious leaders at the words of Peter, we will see a strong rejection and they will seek ways to stop it or do away with those giving it rather than listen to the truth. And one of things that will happen is Sunday laws will come into effect. Whether the leaders of the world, spurred on by the Image or the Beast itself or even the false Christ, declaring this needs to be done, and people will think it is for the 'common good' or from God. So we see how the latter rain, the loud cry, and the Sunday laws, all come into play. As they do, God?s people who have received the outpouring of the Holy Spirit with with power and conviction, spread the truth and proclaim the Sabbath with great power.
We see what the SOP tells us on this:

"And at the commencement of the time of trouble, we were filled with the Holy Ghost as we went forth and proclaimed the Sabbath more fully. This enraged the churches and nominal Adventists, as they could not refute the Sabbath truth. And at this time God?s chosen all saw clearly that we had the truth, and they came out and endured the persecution with us. I saw the sword, famine, pestilence, and great confusion in the land." {EW 33.2}

Now its here as we see in the events unfolding in front of us, and we see what Christ says about just before His second coming when people need to be alert.
Lets turn to Matthew 24:45-49:

Matthew 24:45-49
45 Who then is a faithful and wise servant, whom his lord hath made ruler over his household, to give them meat in due season? 46 Blessed [is] that servant, whom his lord when he cometh shall find so doing. 47 Verily I say unto you, That he shall make him ruler over all his goods. 48 But and if that evil servant shall say in his heart, My lord delayeth his coming; 49 And shall begin to smite [his] fellow servants, and to eat and drink with the drunken; 50 The lord of that servant shall come in a day when he looketh not for [him], and in an hour that he is not aware of,

There is the faithful servant who under the outpouring of the Holy Spirit prepares, but there are other servants who say to themselves, "My Lord delayeth His coming." Do you think this servant is ready, I think not, and worse they fight with the faithful ones doing them harm. We find more on what we will face in John 16:2.

John 16:2 "They shall put you out of the synagogues: yea, the time cometh, that whosoever killeth you will think that he doeth God service."

So we see they will try to wipe out Gods people thinking they are doing what God wants, and the "world shall rejoice".

But lets look at Gods promise to His faithful. Lets turn to John 16:20:

John 16:20
"Verily, verily, I say unto you, That ye shall weep and lament, but the world shall rejoice: and ye shall be sorrowful, but your sorrow shall be turned into joy. "

It is out of this little time of trouble that God?s remnant people will emerge, who give the loud cry and call out the last people out of Babylon, and speak fully of what God made for man at Creation, the Sabbath. We are there my brothers and sisters, we are there. Lets not hesitate to ask for the outpouring of the Holy Spirit and be ready for the effects of the Holy Spirit as we come to the last days.