In Revelation 8:1–6 the Lord Jesus Christ made clear to John (and so to his readers) that God hears the prayers of his people. In response to those prayers, he now has seven angels prepare to blow their trumpets and hence to sound the alarm that the Lord is approaching to fight for his people. Each trumpet blast produces action in which the Lord makes clear his displeasure at how his people are treated.
7 The first angel blew his trumpet, and there followed hail and fire, mixed with blood, and these were thrown upon the earth. And a third of the earth was burned up, and a third of the trees were burned up, and all green grass was burned up.