Within the structure of Revelation, John uses imagery to describe events on earth and in heaven during the coming period of persecution before the return of the Messiah. The first image is of the opening of a document with seven seals, the second is a series of seven angels blowing trumpets, and the last is a series of seven bowls which are upturned as judgment is pronounced.
These are sometimes called the seven “judgements” since they tend to be a judgements, although not all can be described in this way. The fifth seal, for example, is a scene in heaven of those who have been martyred. Some are simply events that set up the final conflict between the Beast and Christ.
The difficulty in interpreting these judgements is that the language is highly symbolic. John is describing these events in metaphorical language. As I have said, reading Revelation is like looking at a political cartoon from another culture and time. I need to understand the cultural and historical cues in the imagery in order to understand John’s original intention. For an American, baseball and cowboy movies are “image sets” which virtually everyone understands.
Greg Beale suggests that there are several potential “image sets” which inform John’s descriptions used in the vision (Revelation 370f). Nero’s persecution of Christians after the great fire in Rome is a good possibility, as are two major earthquakes in the Lycus valley in A.D. 17 and 60. An often overlooked event for the study of Revelation is the eruption of Mount Vesuvius in 79. This is intriguing especially for the fifth trumpet, since the descriptions of that catastrophe in contemporary literature sound quite a bit like John’s description of the opening of the Abyss. Beale also mentions a great famine in A.D. 92, an event which would have been fresh in the minds of those living in Asia Minor.
In fact, these are all well-known events to Christians living in Asia Minor in the 90’s A.D. If John alluded to the terror of a major earthquake in the Lycus Valley in 60, it is possible some hearing Revelation for the first time experienced that earthquake in their youth or heard stories from their parents about it. Personal experience is what makes a metaphor “work,” John used language that resonated with his readers.
To Beale’s list I would add the fall of Jerusalem, since the burning of Jerusalem and the Temple was a traumatic loss to the Jews, even to Christian Jews. I think that the original readers of Revelation were Jewish Christians. As followers of Jesus, the fall of Jerusalem would a confirmation of Jesus’ own predictions, but it was nonetheless a crisis of faith. Undoubtedly stories of those final days circulated among Jewish Christians who may have lost family members in Rome’s military action.
Finally, the main source for all of John’s imagery is the Hebrew Bible. He draws on the language of the curses of the Law for the three cycles of judgments. For example, Leviticus 26:21-26 as background to the four horsemen. The Exodus narrative provides some of the imagery for the trumpets. It is easy enough to hear echoes of the plagues in the descriptions of the first four trumpets.
When John describes a coming time of great persecution, he is talking about present realities. In my opinion it is the growing persecution of Christianity under Domitian as well as internal struggles caused by the success of the church among the Gentiles. John is using creative language drawn from well-known events of his day; but he also talking “through” the events to their ultimate fulfillment in the end times.