1 For, behold, in those days, and in that time, when I shall bring again the captivity of Judah and Jerusalem,
2 I will also gather all nations, and will bring them down into the valley of Jehoshaphat, and will plead with them there for my people and for my heritage Israel, whom they have scattered among the nations, and parted my land.
The Holy Bible, Zechariah 14:1-3
1 Behold, the day of the Lord cometh, and thy spoil shall be divided in the midst of thee.
2 For I will gather all nations against Jerusalem to battle; and the city shall be taken, and the houses rifled, and the women ravished; and half of the city shall go forth into captivity, and the residue of the people shall not be cut off from the city.
3 Then shall the Lord go forth, and fight against those nations, as when he fought in the day of battle.
The Holy Bible, Zechariah 14:12-16
12 And this shall be the plague wherewith the Lord will smite all the people that have fought against Jerusalem; Their flesh shall consume away while they stand upon their feet, and their eyes shall consume away in their holes, and their tongue shall consume away in their mouth.
13 And it shall come to pass in that day, that a great tumult from the Lord shall be among them; and they shall lay hold every one on the hand of his neighbour, and his hand shall rise up against the hand of his neighbour.
14 And Judah also shall fight at Jerusalem; and the wealth of all the heathen round about shall be gathered together, gold, and silver, and apparel, in great abundance.
15 And so shall be the plague of the horse, of the mule, of the camel, and of the ass, and of all the beasts that shall be in these tents, as this plague.
16 And it shall come to pass, that every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the Lord of hosts, and to keep the feast of tabernacles.
New Testament Student Manual, Revelation 9:15-16
John recorded in Revelation 9:15-16 that terrible destruction will be unleashed by God’s messengers during the last days before the Savior’s Second Coming. John declared that “two hundred hundred thousand” (200,000,000) men of war will fight in the battle of Armageddon (verse 16). We do not know whether that number is symbolic or literal. John also recorded that “the third part of men” will be slain (verse 15). Of this prophecy, Elder Bruce R. McConkie stated, “The slain will be a third of the inhabitants of the earth itself, however many billions of people that may turn out to be” (Millennial Messiah, 453).
Journal of Discourses, Orson Pratt 15:41
If you want to know about the time when the sun and moon are to be darkened, and when the stars will no longer give any light, and when there will be total darkness over all the face of the earth, here is an event predicted so that you cannot mistake. When you see the nations of the earth, especially the heathen nations, and also those north of Jerusalem–the great nation of Russia and other nations on the continent of Asia, together with many in Europe, gather up against Jerusalem after the Jews have returned and rebuilt their city and Temple, and when their armies become exceeding great multitudes in the valley of decision, then you may look for the Lord to come down with his mighty ones, and for the constellations of heaven to be darkened.
Journal of Discourses, Orson Pratt 18:7
After awhile, when tens of thousands of them have gathered and rebuilt their Temple, and reestablished Jerusalem upon its own heap, the Lord will send forth amongst them a tremendous scourge. What will be the nature of that scourge? The nations that live in the regions round about Jerusalem will gather up like a cloud, and cover all that land round about Jerusalem. They will come into the Valley of Jehoshaphat, east of Jerusalem, and they will lay siege to the city. What then? The Lord will raise up two great Prophets, they are called witnesses, in the Revelation of St. John. Will they have much power? Yes, during the days of their prophesying they will have power to smite those who undertake to destroy them, and until their testimonies are fulfilled they will be able to keep at bay all those nations besieging Jerusalem, so that they will not have power to take that city. How long will that be? Three and a half years, so says John the Revelator. If any man hurt them, they shall have power to bring upon that man, nation or army, the various plagues that are there written. They will have power to smite the earth with plague and famine, and to turn the rivers of water into blood. And when they have fulfilled their prophecy, then the nations that have been lying before Jerusalem so long, waiting for an opportunity to destroy the city, will succeed in killing these two Prophets, and their bodies, says John’s revelations, will lie in the streets of Jerusalem three days and a half after they are killed. What rejoicing there will be over the death of these men! Those who have been waiting so long and anxiously for this to take place, will no doubt send gifts one to another, and if the telegraph wires are not destroyed, they will telegraph to the uttermost parts of the earth that they have succeeded in killing the two men who had so long tormented them with plagues, turning the waters onto blood, etc. But by and by, right in the midst of their rejoicing, when they think the Jews will now certainly fall a prey to them, behold there is a great earthquake, and in the midst of it these two Prophets rise from the dead, and they hear a voice up in the heavens saying–”Come up hither;” and they immediately ascend in the sight of their enemies. What next? Notwithstanding all this, those nations will be so infatuated, and so determined to persecute the people of God–as much so as Pharaoh and his army in ancient days–that they will say–”Come, now is the time to pitch into the Jews and destroy them.” And they will commence their work of destruction, and they will succeed so far as to take one half the city, and while they are in the very act of destroying Jerusalem, behold the heavens are rent, and the Son of God with all the heavenly hosts appears, and he descends and rests upon the summit of the Mount of Olives, which is before Jerusalem on the east. And so great will be the power of God that will then be made manifest, that the mountain will divide asunder, half going towards the south, and half towards the north, producing a great valley going east and west, from the walls of Jerusalem eastward.