Smith's Bible Dictionary
Harmagedon(hill of Megiddo), (Revelation 16:16) in the Revised Version for Armageddon. The change is chiefly Har , hill, in place of Ar , city.
International Standard Bible Encyclopedia
HAR-MAGEDONhar-ma-ged'-on (Harmagedon from Hebrew har meghiddo, "Mount of Megiddo"; the King James Version Armageddon): This name is found only in Revelation 16:16. It is described as the rallying-place of the kings of the whole world who, led by the unclean spirits issuing from the mouth of the dragon, the beast and the false prophet, assemble here for "the war of the great day of God, the Almighty." Various explanations have been suggested; but, as Nestle says (HDB, s.v.), "Upon the whole, to find an allusion here to Megiddo is still the most probable explanation." In the history of Israel it had been the scene of never-to-be-forgotten battles. Here took place the fatal struggle between Josiah and Pharaoh-necoh (2 Kings 23:29 2 Chronicles 35:22). Long before, the hosts of Israel had won glory here, in the splendid victory over Sisera and his host (Judges 5:19). These low hills around Megiddo, with their outlook over the plain of Esdraelon, have witnessed perhaps a greater number of bloody encounters than have ever stained a like area of the world's surface. There was, therefore, a peculiar appropriateness in the choice of this as the arena of the last mighty struggle between the powers of good and evil. The choice of the hill as the battlefield has been criticized, as it is less suitable for military operations than the plain. But the thought of Gilboa and Tabor and the uplands beyond Jordan might have reminded the critics that Israel was not unaccustomed to mountain warfare. Megiddo itself was a hill-town, and the district was in part mountainous (compare Mt. Tabor, Judges 4:6, 12; "the high places of the field," 5:18). It will be remembered that this is apocalypse. Har-Magedon may stand for the battlefield without indicating any particular locality. The attempt of certain scholars to connect the name with "the mount of congregation" in Isaiah 14:13 (Hommel, Genkel, etc.), and with Babylonian mythology, cannot be pronounced successful. Ewald (Die Johan. Schrift, II, 204) found that the Hebrew forms of "Har-Magedon" and "the great Rome" have the same numerical value-304. The historical persons alluded to in the passage do not concern us here.
W. Ewing