Who was Gog?
In the Hebrew Bible or Christian Old Testament, Gog was the prince of Rosh, Meshech and Tubal (Ezekiel 38:2 f; 39:1-16). His territory was known as the land of Magog, and he was the chief of those northern hordes who were to make a final onslaught upon Israel while enjoying the blessings of the Messianic age. He has been identified with Gagi, ruler of Sakhi, mentioned by Ashurbanipal, but Professor Sayce thinks the Hebrew name corresponds more closely to Gyges, the Lydian king, the Gugu of the cuneiform inscriptions. According to Ezekiel's account Gog's army included in its numbers Persia, Cush, Put, Gomer or the Cimmerians, and Togarmah, from the extreme North. They are represented as a vast mixed horde from the far-off parts of the North, the limits of the horizon, completely armed and equipped for war.
They were to come upon the mountains of Israel and cover the land like a cloud. Their purpose is plunder, for the people of Israel are rich and dwell in towns and villages without walls. His coming, which had been prophesied by the seers of Israel, shall be accompanied by a theophany and great convulsions in Nature. A panic shall seize the hosts of Gog, rain, hailstones, pestilence, fire and brimstone shall consume them.
Their bodies shall be food for the birds, their weapons shall serve as firewood for seven years and their bones shall be buried east of the Jordan in Hamon-gog and thus not defile the holy land. The fulfillment of this strange prophecy can never be literal. In general it seems to refer to the last and desperate attempts of a dying heathenism to overturn the true religion of Yahweh, or make capital out of it, profiting by its great advantages.
(3) In Revelation 20:7 Satan is let loose and goes to the four corners of the earth, Gog and Magog, to muster his hosts for the final struggle against God. In Ezekiel the invasion of Gog occurs during the Messianic age, while in Revelation it occurs just at the close of the millennium. In Ezekiel, Gog and Magog are gathered by Yahweh for their destruction; in Rev they are gathered by Satan. In both cases the number is vast, the destruction is by supernatural means, and is complete and final
IBSE, (in the public domain) with minor edits.