Satan’s opposition to the people of God is a recurring theme in the previous chapters (Revelation 12:17; Revelation 13:7; Revelation 17:6). It is striking that in the present passage, Christ’s army carries no weapons. For the battle is the Lord’s (Revelation 19:15).
19 And I saw the beast and the kings of the earth with their armies gathered to make war against him who was sitting on the horse and against his army.