Jeremiah 31

As Jeremiah prophecies concerning the gathering and work of Israel and Judah in the last days, he speaks of the role and responsibility of Ephraim in this work saying -

"For there shall be a day, that the watchmen upon the mount Ephraim shall cry, Arise ye, and let us go up to Zion unto the LORD our God."  (Old Testament | Jeremiah 31:6)

In my mind, watchmen would be the Lord's prophets, where Zion are -

"...they were of one heart and one mind, and dwelt in righteousness; and there was no poor among them."  (Pearl of Great Price | Moses 7:18)

...and mount Ephraim is His holy house were Ephraims administers priesthood ordinances.  The return of Israel and Judah will not necessarily be to a location but to an acceptance of the true gospel of Jesus Christ, thus -

"They shall come with weeping, and with supplications, will I lead them: I will cause them to walk by the rivers of waters in a straight way, wherein they shall not stumble: for I am a father to Israel, and Ephraim is my firstborn."  (Old Testament | Jeremiah 31:9)

As Isaiah taught, Jesus Christ is the father of Israel with Israel eventually being recipients of exaltation.  And Ephraim, as the firstborn, is responsible to take the lead and care for the family of Israel for in the last days -

"Is Ephraim my dear son? is he a pleasant child? for since I spake against him, I do earnestly remember him still: therefore my bowels are troubled for him; I will surely have mercy upon him, saith the LORD."  (Old Testament | Jeremiah 31:20)

It will be the role of Ephraim to take the lead in building His kingdom in the last days.