The running of the four-horse race begins from Christ's ascension (Mark 16:19-20) and continues through the entire age of the church, to Christ's coming back. Beginning with the first century, the gospel has been spreading throughout these twenty centuries. War among the human race has also been proceeding simultaneously. War has always caused famine, and famine has issued in death. All these will continue until the end of this age. When the seventy weeks in Daniel are completed, the four-horse race will be over. The gospel, war, famine, and death will cease.
The fifth seal is the cry of the martyred saints (Rev. 6:9-11).
It is the cry to avenge their blood (Rev. 6:10).
The fifth seal is the cry of those martyred because of the word of God and because of their testimony (Rev. 6:9b), including the martyrs of the Old Testament (Matt. 23:34-36).
These martyrs are underneath the altar. In figure, the altar is in the outer court of the tabernacle and the temple, and the outer court signifies the earth. Hence, underneath the altar signifies underneath the earth (Matt. 12:40), where paradise, the comfortable section of Hades (Luke 16:22-23) that keeps the souls of the martyred saints is (Luke 23:43).
These martyred saints cry with a loud voice, saying, "How long, O sovereign Lord, holy and true, will You not judge and avenge our blood on those who dwell on the earth?" (Rev. 6:10). "How long" signifies that the martyrs have been waiting in paradise for quite a long time already.