“And the Lord said unto Joshua, See, I have given into thine hand Jericho, and the king thereof, and the mighty men of valour. And ye shall compass the city, all ye men of war, and go round about the city once. Thus shalt thou do six days. And seven priests shall bear before the ark seven trumpets of rams’ horns: and the seventh day ye shall compass the city seven times, and the priests shall blow with the trumpets. And it shall come to pass, that when they make a long blast with the ram’s horn, and when ye hear the sound of the trumpet, all the people shall shout with a great shout; and the wall of the city shall fall down flat, and the people shall ascend up every man straight before him.” ~ Joshua 6:2-5
The central and ultimate purpose of Revelation is to expose and destroy the deception of false religion and carnal sinful man (Babylon and the beast she rides) so that people can get free. Once free, people can truly crown Jesus Christ as their King of kings and Lord of Lords. And the proof of Jesus being their Lord will show in holy living and a life devoted to his service.
The sounding of the seven trumpets, like the final day of the siege of Jericho, is the final call of God’s people together to worship and spiritual battle. Like with Jericho, the purpose is to march against the walls of the city and sound the trumpets against them. So also the trumpets are sounded against the spiritual walls of Babylon.
Jericho had to first be destroyed to conquer the promised land. So the influence of Babylon must also be destroyed for people to become complete conquerors over the deception of false Christianity and paganistic lies. No one can truly say Jesus Christ is completely my Lord except they are fully submitted to the Holy Spirit’s will: and the deception of Babylon stands in the way of that.
So in Revelation 8 and the opening of the seventh seal, a ministry anointed by the Holy Ghost begins the work of sounding the gospel trumpet against the deceptive walls of Babylon.
The final end of Babylon’s walls will happen (like with Jericho) when after a long sounding of the seventh trumpet, wrath will be shouted out in the form of seven vials of God’s wrath.