Atonement for many
Saying to the sixth angel which had the trumpet, (a)"Loose the four angels which are bound in the great river (b)Euphrates".
And the (c)four angels were loosed, which had been prepared for the hour, and a day, and a month, and a year, in order to (d)slay the third part of men.
(a) The four angels bound; these angels may not be of Heaven, according to some commentators, but of the fallen ones of earlier Ages, described in Scripture. We know from various references that these and many others are bound for later judgement by Jehovah / Christ, (2Pet. 2:4). These four however are bound "on the Euphrates", for a special purpose. All of the fallen angels (those that followed Satan have the purpose of destroying humankind from Adam), and in this case in point, their great malevolence maybe held in store by God for His purpose. However, they may be angels of service to Jehovah, who have been holding back great forces of evil.
As we have seen earlier, the great sacrifice of Jehovah in Christ has brought to naught all the workings of Satan, and the great symbol of that work is the golden incense alter, which is "before God", (V.13). That great completed work allows for the first time the release of the wrath of God on the nations of the world (Jer. 46), which could not have been previous in time. The Son had to become The Atonement for many, the number of the Gentiles had to be complete in the Body of Christ, (some pre Acts 28, some post Acts 28, with different inheritance), (Acts 15:17) & (Rom. 11:25). Heavenly creation had to witness the Perfect Love of the Father in Christ, (Eph.3:10). All of this brought to culmination the perfect order from the horns of the golden alter to release the angels, and the wrath of Jehovah God to Earth, on unrepentant, and evil mankind.
Many people are disturbed by the thought of a loving God releasing such horror (wrath) on the nations of the world. Many teachers try to reassure people that Israel is the intended target. In the opinion of the writers that is a feasible concept, but in the light of the rest of Revelation it is hard to be absolutely sure. Also, many teachers do not believe the Bible anyway, and teach a mix of tradition and their own opinion. They would accuse the writers of the same. However, we trust the Bible and the Holy Spirit alone, and will not write or say anything regarding Scripture of which we are not truly, and prayerfully convinced. In that ethos, the Word in Jer. 46:10 says explicitly, referring to the Revelation period, "this is the Day of Jehovah Zebaoth, a day of vengeance". In verse 46:1 the meaning is clear, it is against the Gentiles, (The Gentiles in point here in this reference in Jer. 46 are the adjacent Gentile nations who have been so problematic for Israel historically, however, because both genetically and in terms of opposing Religions, these nations in effect have spread to most parts of the world. As is seen in current events , the smallest news item or trouble in Israel has repercussions world-wide; so that the inevitability in the minds of the writers is that the effects of action on the adjacent nations by Jehovah Zebaoth effects the world as we know it by transferred consequence).
Some teachers sincerely confuse the Satanic oppression of Israel with the above, as the writers believe they are partly simultaneous. The point is that Jehovah Zebaoth's (God of all the world, dealing with the world) Day has not yet ever taken place. All of Revelation was given to John who was "in the spirit in the Lord's Day", (Rev. 1:10), so that detail links to Jer. 46, and many other references to "The Day of Jehovah", in other places in Scripture; and the people God is dealing with are not in this present Age, although they may go through into the next, if not translated. This Age has the immeasurable privilege on offer of trusting in Christ alone for Salvation (Acts 4:12), and being preserved from the wrath to come.