Most are familiar with the Three Angels Messages that began in 1844, which came to sound the warning of the coming judgment on this earth.  The following are excerpts and overview from the book The Seven Angels by F. T. Wright.
 

       The first angel, equipped with the everlasting gospel which is the unlimited power of God to save from sin, offered deliverance from spiritual bondage to every nation on the earth. . . Unfortunately, due to the depths of spiritual apostasy into which the churches had sunk, the response was very poor.  The majority chose to reject the message, preferring instead to ridicule and persecute those who presented it.  [This movement was called the Millerite Movement, which called the people out of the churches in 1844.]
 
 

        One role of the second angel is to declare the fallen spiritual condition of those who have rejected the truth so the believers will plainly understand that God is no longer with the apostate church organizations, even though their leaders boldly claim to be still walking in the light of God's presence in full enjoyment of His favor.  This not only removes all fear of separation from the established but decadent church organizations; it actually shows that the step is essential.

        When the time came for the added light of the second angel, it was not given through William Miller.  A new man was chosen for the proclamation of the message, he was Charles Fitch.  Later, God used Samuel Snow to inaugurate the midnight cry, the final phase of the second angel's message.
 
 

        The third angel reveals the ultimate outworking of the acceptance on one hand and the rejection on the other, of the first angel's message.  For those who gladly received the saving light from heaven, the seal of God and a place in His kingdom is assured if they follow on in the knowledge of God.  But those who deny the gospel will receive the mark of the beast, the number of his name, and the total destruction by fire which will befall such unfortunate people.

        . . . New leaders were called by God to serve at this time.  O.R.L. Crosier and Hiram Edson were the first to receive light from the third angel.  As they were crossing a corn field in the early hours of the morning following the great disappointment, they saw that Christ had entered the most holy place of the heavenly sanctuary, and that this, not His expected return to the earth, was what the prophecy predicted.  God's word had not failed.
 

        But the decline into Laodiceanism which followed the establishment of the third angel's movement brought yet another crisis which was met by God's sending the Revelation 18 or fourth angel.  This angel brings the light of the third angel with a clarity and power not fully seen previously.  Though unfortunately rejected in 1888, he is presently with us again [1988], and this time we believe that his work will be successful.  [Unfortunately this message was again rejected by the structure church, and was spewed out and went into full apostasy.   Church Apostasy ]
 

      . . . That this angel is just as much the the symbol of a movement as the previous four, is assured by the interpretation provided for us in the Spirit of Prophecy, of Revelation  14:16, which reads:

        "And another angel came out of the temple, crying with a loud voice to Him who sat on the cloud, 'Thrust in your sickle and reap, for the time has come for you to reap, for the harvest of the earth is ripe.'"

        When describing events to transpire after the close of probation, the Lord, through His chosen servant, said:  "Then Jesus will have the sharp sickle in his hand, (Revelation 14:14) and then the saints will cry day and night to Jesus on the cloud,  thrust in His sharp sickle and reap."  A Word to the Little Flock, 12.  Back on the Cloud

        The one difference between this and the previous movements will be that no messengers are involved.   Once probation is closed, no further warning voices will call men to repentance.  The time will have come for a different work altogether, and it will be performed through a people so scattered and isolated from each other, that no positions of responsibility toward other believers will be held by anyone.  Nevertheless, it will be a definite body of people doing exactly what the Lord has designed that they shall.   Behold the Bridegroom Cometh . . .

        The lesson of implicit obedience must be learned so fully by those who will number the 144,000, that the Lord will be able to trust them as completely as He could Christ.  It will not be an easy task to achieve this level of obedience. . .

        There is no human language which can adequately describe the pressure that the saints will feel at this time, when, at all costs they must live by every word which proceeds from the Lord.  Obedience is to be the only consideration.  They know that Christ is the Harvester while their task is to demonstrate that the only possible solution to the manifold woes which will be increasingly felt by the wicked, is found with God, the infinite Problem-solver.

    Thus, when they call upon Jesus to thrust in His sickle and reap, they are really confirming that they recognize Christ's role on the one hand and their true position on the other.  They are saying in effect that there is no pressure which will induce them to act from any other consideration but obedience to the word of God.  What He says they will do, nothing more and nothing less.  They will make no attempt to do God's work for Him as the multitudes around are doing.  They are declaring that they will relate themselves to the hour of temptation exactly as Jesus did in the wilderness.

    It is because they will be as established in this stand as Christ was that they will succeed where every other movement in the past has failed.  Whereas the members of all previous movements have taken over the work of attempting to build God's kingdom for Him, they will leave the work of harvesting and kingdom building entirely to Him.  The great victory they will gain will be achieved more by doing nothing than by doing something.  This is the most difficult kind of victory for anyone to gain.

        "The season of distress and anguish before us will require a faith that can endure weariness, delay, and hunger--a faith that will not faint though severely tried.  The period of probation is granted to all to prepare for that time.  Jacob prevailed because he was persevering and determined.  His victory is an evidence of the power of importunate prayer.  All who will lay hold of God's promises, as he did, and be as earnest and persevering as he was, will succeed as he succeeded.  Those who are unwilling to deny self, to agonize before God, to pray long and earnestly for His blessing, will not obtain it.  Wrestling with God--how few know what it is!  How few have ever had their souls drawn out after God with intensity of desire until every power is on the stretch.  When waves of despair which no language can express sweep over the suppliant, how few cling with unyielding faith to the promises of God."  The Great Controversy, 621.
 

        Just as certainly as the previous five angels each symbolize a movement of people doing God's will under His protection, blessing, and direction, so does the sixth angel.  This body of people will do its work when the fifth angel has completed his at the closing up of Jacob's trouble.

        Let us then assemble the available facts about this angel and the movement he represents.  In the first case, he is said to come out of the ". . .temple which is in heaven. . ."  Revelation 14:17.  This is true of the fifth angel also and the sense in which God's people, the wise virgins, otherwise known as the 144,000, go into and come out of the most holy place in heaven, has already been demonstrated.  It is in the spiritual and not physical sense that this is accomplished, for the 144,000 will not make a literal entry into the heavenly temple until after their translation.  It was when, in response to the message given in the midnight cry, that the virgins understood the position and work of Christ in the most holy place in heaven, and followed Him by faith as He went in before God, even though they were physically still down on earth.

        Since that time, every believer in Jesus who understands the ministry of Christ in the sanctuary above, and enters into the blessings which that ministry offers, is with his glorious High Priest in the temple of God in heaven.  While Christ remains there, so by faith will they, but when He leaves, they will come out with Him, for the 144,000 ". . .follow the Lamb wherever He goes. . ." Revelation 14:4.  Thus, when the ministry in the most holy is finished, and Christ lays off His priestly attire in exchange for His kingly robe and crown, Red Robes   and then leaves the temple to journey to this earth, the believers in Jesus will come out with their spotless High Priest as they continue to follow Him in their spiritual walk of faith.  It is for this reason that both the fifth and sixth angels are said to come out of the temple which is in heaven.
 

        "All the judgments upon men, prior to the close of probation, have been mingled with mercy. The pleading blood of Christ has shielded the sinner from receiving the full measure of his guilt; but in the final judgment, wrath is poured out unmixed with mercy."  The Great Controversy, 629.

        The command will be given by the seventh angel to the sixth to '. . .Thrust in your sharp sickle and gather the clusters of the vine of the earth, for her grapes are fully ripe.'

        Except in the sense that it cleanses the earth of sin and sinners, and stops the wicked from building up a fearful storm of retribution against themselves, there is no blessing in the wine of God's wrath but only a fearful, death-dealing curse which does not stay its power until its victims are totally annihilated.

        Before the controversy can be resolved, every question of truth and error must be forever settled, this one included.  What sin will do to men and nature, must be revealed in unmasked clarity so that all, both righteous and unrighteous, can see the actual outworking of evil. . . Sin will be exposed in all its hideousness and righteousness will shine forth in its true luster and glory.

        They must resist evil with all the powers the Lord has made available to them, while cultivating every spiritual grace whereby the character of God will eventually reach full maturity in them.

        May everyone who professes to be a believer in Jesus understand the implications of the seven angels' movements and rest not until he is fulfilling his divinely-appointed place and enabling the Lord to thrust in His sharp sickle and gather the harvest of the ages.  Oh!  What unspeakable joy it will be to stand on the right side then!