Some thoughts on this thread. What we know...
1- A preliminary gathering of Judah to Jerusalem will occur when Judah is largely in unbelief as a people
7 And it shall come to pass that the Jews which are scattered also shall begin to believe in Christ; and they shall begin to gather in upon the face of the land; and as many as shall believe in Christ shall also become a delightsome people.
8 And it shall come to pass that the Lord God shall commence his work among all nations, kindreds, tongues, and people, to bring about the restoration of his people upon the earth.
(2 Nephi 30:7-8)
As I have been reading to you to-day, the Jews have got to gather to their own land in unbelief. They will go and rebuild Jerusalem and their temple. They will take their gold and silver from the nations and will gather to the Holy Land, and when they have done this and rebuilt their city, the Gentiles, in fulfillment of the words of Ezekiel, Jeremiah, and other prophets, will go up against Jerusalem to battle and to take a spoil and a prey; and then, when they have taken one-half of Jerusalem captive and distressed the Jews for the last time on the earth, their Great Deliverer, Shiloh, will come. They do not believe in Jesus of Nazareth now, nor ever will until he comes and sets his foot on Mount Olivet and it cleaves in twain, one part going towards the east, and the other towards the west. Then, when they behold the wounds in his hands and in his feet, they will say, “Where did you get them?” And he will reply, “I am Jesus of Nazareth, King of the Jews, your Shiloh, him whom you crucified.” Then, for the first time will the eyes of Judah be opened. They will remain in unbelief until that day. This is one of the events that will transpire in the latter day.
(Journal of Discourses, Wilford Woodruff 15:35)
2- The Jerusalem Temple is built
The work is moving on for the gathering of the Jews to their own land that they may build it up as it was in former times; that the temple may be rebuilt and the mosque of the Muslim which now stands in its place may be moved out of the way; that Jerusalem may be rebuilt upon its original site; that the way may be prepared for the coming of the Messiah, who shall be seen in the midst of those whose ancestors nailed him to the cross, and who, when they see the marks in His hands, shall say in answer to their inquiries, “These are the wounds with which I was wounded in the house of my friends.
(Journal of Discourses, Charles W. Penrose 24:25)
I remember, some time ago, having a conversation with Baron Rothschild, a Jew. …[I told him that] You will build a Temple, for the Lord has shown us, among other things, that you Jews have quite a role to perform in the latter days, and that all the things spoken by your old prophets will be fulfilled, that you will be gathered to old Jerusalem, and that you will build a Temple there; and when you build that Temple, and the time has arrived, ‘the Lord whom you seek will suddenly come to his Temple.'
(Journal of Discourses, John Taylor 18:23)
The Jews dispersed among the Gentiles will not come and sing in the height of Zion, or but very few of them, they will go to Jerusalem. Some of them will believe in the true Messiah, and thousands of the more righteous, whose fathers did not consent to the shedding of the blood of the Son of God, will receive the Gospel before they gather from among the nations. Many of them, however, will not receive the Gospel, but seeing that others are going to Jerusalem they will go also; and when they get back to Palestine, to the place where their ancient Jerusalem stood, and see a certain portion of the believing Jews endeavoring to fulfill and carry out the prophecies, they also will take hold and assist in the same work. At the same time they will have their synagogues, in which they will preach against Jesus of Nazareth, “that impostor,” as they call him, who was crucified by their fathers. 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.
(Journal of Discourses, Orson Pratt 18:7)
3- The Battle of Armageddon events occur and the Jews are converted as a people
44 And then they shall look for me, and, behold, I will come; and they shall see me in the clouds of heaven, clothed with power and great glory; with all the holy angels; and he that watches not for me shall be cut off.
45 But before the arm of the Lord shall fall, an angel shall sound his trump, and the saints that have slept shall come forth to meet me in the cloud.
46 Wherefore, if ye have slept in peace blessed are you; for as you now behold me and know that I am, even so shall ye come unto me and your souls shall live, and your redemption shall be perfected; and the saints shall come forth from the four quarters of the earth.
47 Then shall the arm of the Lord fall upon the nations.
48 And then shall the Lord set his foot upon this mount, and it shall cleave in twain, and the earth shall tremble, and reel to and fro, and the heavens also shall shake.
49 And the Lord shall utter his voice, and all the ends of the earth shall hear it; and the nations of the earth shall mourn, and they that have laughed shall see their folly.
50 And calamity shall cover the mocker, and the scorner shall be consumed; and they that have watched for iniquity shall be hewn down and cast into the fire.
51 And then shall the Jews look upon me and say: What are these wounds in thine hands and in thy feet?
52 Then shall they know that I am the Lord; for I will say unto them: These wounds are the wounds with which I was wounded in the house of my friends. I am he who was lifted up. I am Jesus that was crucified. I am the Son of God.
53 And then shall they weep because of their iniquities; then shall they lament because they persecuted their king.
( Doctrine and Covenants, Section 45:44-53)
23 Thus will I magnify myself, and sanctify myself; and I will be known in the eyes of many nations, and they shall know that I am the Lord.
4- During the Battle of Armageddon events when Christ appears on the Mount of Olives, after the Jews are converted as a people, water comes out from under the temple, the Jews receive the Gospel
4 And his feet shall stand in that day upon the mount of Olives, which is before Jerusalem on the east, and the mount of Olives shall cleave in the midst thereof toward the east and toward the west, and there shall be a very great valley; and half of the mountain shall remove toward the north, and half of it toward the south.
5 And ye shall flee to the valley of the mountains; for the valley of the mountains shall reach unto Azal: yea, ye shall flee, like as ye fled from before the earthquake in the days of Uzziah king of Judah: and the Lord my God shall come, and all the saints with thee.
6 And it shall come to pass in that day, that the light shall not be clear, nor dark:
7 But it shall be one day which shall be known to the Lord, not day, nor night: but it shall come to pass, that at evening time it shall be light.
8 And it shall be in that day, that living waters shall go out from Jerusalem; half of them toward the former sea, and half of them toward the hinder sea: in summer and in winter shall it be.
They have looked upon him whom their fathers pierced, they behold the wounds, they are now convinced that they and their fathers have been in error some eighteen hundred years, and they repent in dust and ashes. The next step for them will be baptism for the remission of their sins. They look upon him whom their fathers pierced and they mourn for him as one who mourns for his only son, and, as Zechariah says, they are in bitterness for him. But repentance alone would not be sufficient, they must obey the ordinances of the Gospel; hence there will be a fountain opened at that time on purpose for baptism. Where will it be opened? On the east side of the Temple. A stream will break out from under the threshold of the Temple, says the Prophet, and it will run eastward, and will probably pass directly through the deep valley made by the parting of the Mount of Olives. It will run eastward, and as you go down from the Temple a few thousand cubits it increases so rapidly that it becomes a great river that cannot be forded. This is the fountain that Zechariah says is open to the inhabitants of Jerusalem and to the house of David for sin and uncleanness. “How is it that” says one? “Water for sin and uncleanness?” Why yes, baptism for the remission of sins. Then the Jews will receive the Gospel and they will be cleansed from all their sins by being baptized in water for their remission. Then will be fulfilled the words of the Prophet Isaiah, when speaking of Jerusalem–”For henceforth there shall no more come into thee the uncircumcised and the unclean.”… And this water which breaks out from the threshold of the Temple, will not only run eastward but westward also, and there will be a great change in the land there, certain portions rising up, others lowered, rough places made smooth and mountains cast down; and half the waters of this spring which will burst forth, will go towards the former sea and half to the other sea; in other words half towards the Dead Sea and half toward the Mediterranean.
(Journal of Discourses, Orson Pratt 18:7)
5- The major gathering of the Jews to Israel will be after the conversion of the Jews at Armageddon
29 And I will remember the covenant which I have made with my people; and I have covenanted with them that I would gather them together in mine own due time, that I would give unto them again the land of their fathers for their inheritance, which is the land of Jerusalem, which is the promised land unto them forever, saith the Father.
30 And it shall come to pass that the time cometh, when the fulness of my gospel shall be preached unto them;
31 And they shall believe in me, that I am Jesus Christ, the Son of God, and shall pray unto the Father in my name (at Armageddon).
32 Then shall their watchmen lift up their voice, and with the voice together shall they sing; for they shall see eye to eye.
33 Then will the Father gather them together again, and give unto them Jerusalem for the land of their inheritance.
34 Then shall they break forth into joy—Sing together, ye waste places of Jerusalem; for the Father hath comforted his people, he hath redeemed Jerusalem.
35 The Father hath made bare his holy arm in the eyes of all the nations; and all the ends of the earth shall see the salvation of the Father; and the Father and I are one.
36 And then shall be brought to pass that which is written: Awake, awake again, and put on thy strength, O Zion; put on thy beautiful garments, O Jerusalem, the holy city, for henceforth there shall no more come into thee the uncircumcised and the unclean.
37 Shake thyself from the dust; arise, sit down, O Jerusalem; loose thyself from the bands of thy neck, O captive daughter of Zion.
38 For thus saith the Lord: Ye have sold yourselves for naught, and ye shall be redeemed without money.
39 Verily, verily, I say unto you, that my people shall know my name; yea, in that day they shall know that I am he that doth speak.
(3 Nephi 20:29-39)
27 Yea, the work shall commence among all the dispersed of my people, with the Father to prepare the way whereby they may come unto me, that they may call on the Father in my name (3 Nephi 20:31).
28 Yea, and then shall the work commence, with the Father among all nations in preparing the way whereby his people may be gathered home to the land of their inheritance.
(3 Nephi 21:27-28)
6- All this must happen before Christ makes his final appearance in Glory
Judah must return, Jerusalem must be rebuilt, and the temple, and water come out from under the temple, and the waters of the Dead Sea be healed (At Armageddon appearance before Coming in Glory). It will take some time to rebuild the walls of the city and the temple, Etc.; and all this must be done before the Son of Man will make his appearance (Coming in Glory)...
(HC, Joseph Smith 5:337)
7- At some point, baptisms for the dead will occur in the Jerusalem Temple. It is unclear if this will be pre/post the Battle of Armageddon events.
36 For it is ordained that in Zion, and in her stakes, and in Jerusalem, those places which I have appointed for refuge, shall be the places for your baptisms for your dead.
37 And again, verily I say unto you, how shall your washings be acceptable unto me, except ye perform them in a house which you have built to my name?
(Doctrine and Covenants, Section 124:36-37)