Just after the seven years of tribulation are completed, Christ will come to the earth, to a place called Armageddon where all the armies of the worlds will come together for war.  Here is how the book of Revelation describes what will happen.

Revelation 19:11-21

And I saw heaven opened; and behold, a white horse, and He who sat upon it is called Faithful and True; and in righteousness He judges and wages war. 12 And His eyes are a flame of fire, and upon His head are many diadems; and He has a name written upon Him which no one knows except Himself. 13 And He is clothed with a robe dipped in blood; and His name is called The Word of God. 14 And the armies which are in heaven, clothed in fine linen, white and clean, were following Him on white horses.

And from His mouth…