War in Heaven

"Now war arose in heaven, Michael and his angels fighting against the dragon. And the dragon and his angels fought back, but he was defeated and there was no longer any place for them in heaven. And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world--he was thrown down to the earth, and his angels were thrown down with him." (Revelation 12:7-9 - English Standard Version)

In verse seven, John's focus shifts from the earth to heaven. This war in heaven will occur around the middle of the Tribulation. Satan will know that his time is running out. He will seek again to take by force the throne of heaven. The archangel, Michael, and the angelic army of heaven will oppose him. A great spiritual battle will take place between the angels of light and the angels of darkness.

Satan and the demons will be defeated and will conclusively be cast out of heaven. Satan has been allowed to come before God and accuse God's children. This is what he did to Job. (Job 1:6) It is what he is doing now, but at the middle of the Tribulation, this will be brought to and end.