This topic concerns the future Attack on Jerusalem, which Jesus warned about in the Gospels.
“When you see Jerusalem being surrounded by armies, you will know that its desolation is near. Then let those who are in Judea flee to the mountains, let those in the city get out, and let those in the country not enter the city. Lk. 21:20-21
The Attack on Jerusalem is also described in the Revelation in the description of the Fourth Trumpet where we are told that one-third of Israel will be struck down.
The fourth angel sounded his trumpet, and a third of the sun was struck, a third of the moon, and a third of the stars (the sun, moon, and stars represent Israel), so that a third of them turned dark. A third of the day was without light, and also a third of the night. Rev. 8:12
Although, these verses do not mention Israel directly, we know that the events of the Fourth Trumpet are referring to an attack on Israel based on the description of how a third of the sun, moon, and stars will be struck. In the Scriptures, the sun, moon, and stars are used to represent Israel. This is first seen in the story of the patriarch Joseph who had a dream in which the original family of Israel is described as the sun, the moon, and the twelve stars. The sun, the moon, and 1the twelve stars are also used to portray Israel in the Revelation itself.
A great sign appeared in heaven: a woman (Israel) clothed with the sun, with the moon under her feet and a crown of twelve stars (the Twelve Tribes of Israel) on her head. She was pregnant and cried out in pain as she was about to give birth… She gave birth to a son, a male child (Jesus), who “will rule all the nations with an iron scepter.” And her child was snatched up to God and to his throne. Rev. 12:1-2, 5
In these verses, the sun, moon, and twelve stars are an obvious reference to Israel, which is the same way that Israel is depicted in the events of the Fourth Trumpet when a third of Israel will be struck. The one-third figure seems to be contradicted by Zechariah who tells us that two-thirds will be struck down in the attack and one-third will be refined like silver.
“In the whole land,” declares the Lord, “two-thirds will be struck down and perish; yet one-third will be left in it. This third I will put into the fire; I will refine them like silver and test them like gold. They will call on my name and I will answer them; I will say, ‘They are my people,’ and they will say, ‘The Lord is our God.’” Zech. 13:8-9
The seeming difference between the one third and two thirds, in the two accounts, can be resolved by looking at what will happen to the survivors of the Attack on Jerusalem. In Zechariah, we read that half of the survivors will be taken from the city.
A day of the Lord is coming, Jerusalem, when your possessions will be plundered and divided up within your very walls. I will gather all the nations to Jerusalem to fight against it; the city will be captured, the houses ransacked, and the women raped. Half of the city will go into exile, but the rest of the people will not be taken from the city. Zech. 14:1-2
Jesus, similarly said that half of the survivors will be taken, and the others left.
“It will be just like this on the day the Son of Man is revealed. On that day no one who is on the housetop, with possessions inside, should go down to get them. Likewise, no one in the field should go back for anything. Remember Lot’s wife! Whoever tries to keep their life will lose it, and whoever loses their life will preserve it. I tell you, on that night two people will be in one bed; one will be taken and the other left. Two women will be grinding grain together; one will be taken and the other left.” “Where, Lord?” they asked. He replied, “Where there is a dead body, there the vultures will gather.” Lk. 17:30-37
When the disciples asked Jesus, “Where will they be taken to?”, He told them that they would be taken to where the vultures gather, which is a description of people being killed and their bodies being left unburied. From the above, we can conclude that when Jerusalem is Attacked, one-third will be killed in the initial battle as described in the Revelation. Of the remaining survivors, half (another one third) will be taken and killed in exile, which accounts for the two-thirds total killed as prophesied by Zechariah. The other surviving third will escape the attack and will be refined like silver.
(To read more about the Attack on Jerusalem, click here: Is the Attack on Jerusalem a Past Event?, and here Revelation Chapter 8)
 Gen. 37:1-11