The vision of chapters 4 and 5 provides the context for the opening of the scroll and its seals, trumpets, and bowls. The scroll itself is not opened until the seven seals are removed and that takes place in dramatic fashion. The content of the scroll itself will be revealed in chapter 8. Each seal is a preliminary judgment to be divulged. Each judgment represents forces throughout history which carry the judicial and redemptive purposes of God through to the end of history.
The vision of the four horsemen is quite the picture of a Halloween entourage. The background of the vision comes from Zechariah's visions of the assorted horses in 1:8-17 and 6:1-8. As is characteristic of John, he modifies his sources with great freedom. The colors red, white, black, and gray of Zechariah appear to have no special significance. In Revelation, however, they correspond to the character of the rider and signify conquest (white), bloodshed (red), famine (black), and death (pale). In Zechariah, the horsemen are sent out to patrol the earth, while in Revelation, their release brings disaster to the earth.
It should be observed that John's vision here is related to Jesus' apocalyptic discourse in the Synoptic Gospels (Matthew, Mark, Luke). Luke records wars and tumultuous times, national strife, earthquakes, famine, and pestilence. In Jewish thought the "age to come" would be preceded by a period of unprecedented woe. Jesus says, "this is but the beginnings of sufferings."
So, who are the four horsemen of the apocalypse? Generally speaking the white horse refers to military conquest, the red horse symbolizes civil war and disorder, the black horse refers to famine, and the pale horse (which approximates the color of a corpse) signifies death. The horsemen logically follow one another-- war and civil disorder lead to famine, scarcity, and disease, and last of all, death. It is important to note that while we may have here a hint of a time of desperate tribulation before the end, the original hearers would have understood that the four horsemen rode even in their day and long before.
The horsemen of the apocalypse have ridden forth and there is a transition in scene. After the first four seals are opened, the fifth seal displays the suffering and the glory of Christian martyrdom. The martyrs in Revelation chapter 6 have offered their lives on account of the "word of God and the testimony of Jesus." It must be remembered that throughout history, those wielding power have been hostile to Christians deeply committed to the lordship of Jesus Christ. It makes one wonder what kind of Christianity is allowed to be free in any society that offers freedom of religion. From beneath the altar, the martyrs issue a plea for vindication. The issue here is not revenge, but a concern for the character of God and his righteousness.
The martyrs are told to remain patient. Those who gave their lives during Nero's persecution will be joined by those who refused to deny their faith before the Emperor Domitian. Like Nero, Domitian is not divine, and many of God's people will go to their death in their refusal to acknowledge Caesar's divinity and lordship.
When the sixth seal is broken all "hell" seems to break loose. The details of this dramatic description of the universe in turmoil are drawn from the context of Jewish apocalyptic documents. They should not be taken with complete literalness. Those who first heard John's words would not have debated the details of the vision.
In delineating the various groups, which rush to find refuge from God's wrath, John wants to emphasize those who have earthly reason to feel secure, but will find themselves in deep trouble. The kings of the earth are those persons in positions of ultimate authority. The princes fall next in line. The chief captains are the military authorities at whose command the Roman armies move into battle. The security of the wealthy and the powerful will be crushed. Confusion will ensue, which is what always happen when a person's security is breached.