How is the Antichrist’s army defeated?

When the armies of the Antichrist and the kings of the earth gather at Armageddon to fight against the Lord, Christ comes riding on a white horse, clothed in a vesture dipped in blood, with a sword going out of His mouth. That sword is not a literal weapon, it is His spoken Word. He does not wage this war with any carnal weapon; His voice alone is enough to smite the nations and rule them with a rod of iron. Revelation 19 shows Him treading the winepress of the fierceness and wrath of Almighty God, and the remnant of the enemy army is slain simply by the sword that proceeds out of His mouth.

The effect of that spoken Word is described vividly in Zechariah. At the mere Word of the Lord, the flesh, eyes, and tongues of His enemies consume away while they are still standing on their feet, and a great tumult from the Lord causes them to turn on one another, every man's hand rising against his neighbor, until confusion finishes what His voice began. Joel describes this same Word as a roar out of Zion so powerful that the heavens and the earth shake at the sound of it.

The slaughter that results is so great that Revelation 14 pictures it as a winepress trodden until blood flows out even to the height of a horse's bridle, for about two hundred miles. The beast and the false prophet who led that army are taken and cast alive into the lake of fire, and the rest of their soldiers lie dead upon the earth. Afterward, an angel calls all the birds of the air to the supper of the great God, to eat the flesh of kings, captains, mighty men, and their horses, the residue of the armies the Lord has judged.

One further detail is given about the state of that army even before the final blow: by the time Armageddon occurs, the earlier plagues will have wrecked the world's infrastructure, waters turned to blood, extreme heat, earthquakes, and darkness, so that electric grids, fuel, and manufacturing are gone. With no way to produce or maintain modern weapons, the armies are forced back to primitive means such as bows, arrows, swords, staves, spears, and shields, which is why the residents of Israel are later able to gather and burn the leftover weapons for seven years. But whatever weapons the enemy carries, it is ultimately the Word out of Christ's mouth, not any human force, that overcomes them, for He is Lord of lords and King of kings and they that are with Him are called, and chosen, and faithful.