As we read through the book, we will notice that several of the judgments mimic after the plagues of Egypt. Once more, this helps to identify the target of John's prophecies. We've consistently seen John make references to apostate Old Covenant Israel, and these Exodus-style "plagues" follow suit. It was during the Exodus that God told the Israelites, if they ever rejected him and his Covenant:
Deuteronomy 28.27-29,60-62: The LORD will strike you with the boils of Egypt, and with tumors and scabs and itch, of which you cannot be healed. The LORD will strike you with madness and blindness and confusion of mind, and you shall grope at noonday, as the blind grope in darkness, and you shall not prosper in your ways. And you shall be only oppressed and robbed continually, and there shall be no one to help you. [...] And he will bring upon you again all the diseases of Egypt, of which you were afraid, and they shall cling to you. Every sickness also and every affliction that is not recorded in the book of this law, the LORD will bring upon you, until you are destroyed. Whereas you were as numerous as the stars of heaven, you shall be left few in number, because you did not obey the voice of the LORD your God.
The first trumpet resembles the seventh plague of Egypt.
Exodus 9.22-26: Then the LORD said to Moses, "Stretch out your hand toward heaven, so that there may be hail in all the land of Egypt, on man and beast and every plant of the field, in the land of Egypt." Then Moses stretched out his staff toward heaven, and the LORD sent thunder and hail, and fire ran down to the earth. And the LORD rained hail upon the land of Egypt. There was hail and fire flashing continually in the midst of the hail, very heavy hail, such as had never been in all the land of Egypt since it became a nation. The hail struck down everything that was in the field in all the land of Egypt, both man and beast. And the hail struck down every plant of the field and broke every tree of the field. Only in the land of Goshen, where the people of Israel were, was there no hail.
In Genesis, God brought about a great flood of water to punish mankind for its gross wickedness. However, following the flood God told Noah that "the waters shall never against become a flood to destroy all flesh". In other words, water was God's primary tool of punishment. But he vowed to not use it again in the destructive manner he did before. Following the flood, we consistently see that God turned from water to fire for his primary tool of punishment. God's fire manifests literally in the destruction of Sodom and Gomorrah, and Damascus, Samaria, Jerusalem, etc., and his fire manifests symbolically in the destruction of God's other enemies as described in the Old Testament prophetic books. [Isaiah 1.31; 5.24; 9.19; 10.16-17; 26.11; 66.15-16; Jeremiah 4.4; 5.14; 11.16; 21.12; 48.45; Lamentations 1.13; 2.3-4; 4.11; Ezekiel 15.4-7; 19.12-14; 21.31; 28.18; 30.14; 38.22; Amos 1.4-2.5; 7.4; Obadiah 1.18; Micah 1.4; Nahum 1.6; 3.15; Zephaniah 1.18; 3.8; Zechariah 9.4; 11.1; Malachi 4.1-3]
Here John sees the fire of God's wrath fall down upon apostate Israel, describing in the same fantastic symbolism of the Old Testament prophets, and combined with imagery drawn from the seventh plague of Egypt.