Removing the parenthetical asides from this long and complex sentence reduces it to its crucial core: After Israel is scattered and persecuted, “the day will come” when they will begin to believe “these things,” meaning the mission of the Atoning Messiah. This concept is, as Nephi understands it, one of Isaiah’s central messages. It comprises the Messiah’s birth, mission, atonement, and death, as well as the triumphant Messiah’s return that will restore Israel to its honored place as Yahweh’s people.
Narrative: Nephi appears to be recasting the information about those who “gathered together to fight against the apostles of the Lamb” (1 Ne. 11:34; see also 35). That “fight against the apostles” would be the equivalent of “the Lord God hath scourged them by other nations for the space of many generations” in this verse.