The Book of Mormon, 1 Nephi 14:17

17 And when the day cometh that the wrath of God is poured out upon the mother of harlots, which is the great and abominable church of all the earth, whose founder is the devil, then, at that day, the work of the Father shall commence, in preparing the way for the fulfilling of his covenants, which he hath made to his people who are of the house of Israel.

Journal of Discourses, Orson Pratt 18:7

Says one—”How long will this continue?” Until the people are thoroughly warned. At the present time there are some nations who will not permit any religion to be proclaimed within their borders except that which is established by law. When God shall cast down thrones, which he will soon do; when he shall overturn kingdoms and empires, which time is very near at hand, then other governments will be formed more favorable to religious liberty, and the missionaries of this Church will visit those nations.

Journal of Discourses, Orson Pratt 7:29

This war that is now taking place will not result in that dreadful extinction that is foretold in the Book of Mormon, and which will rage among all the nations and kingdoms of the Gentiles, or, in other words, among the nations of Christendom. The one is a war preparatory to the proclamation of the Gospel; the other is a war of terrible destruction, which will not better the condition of those who escape. The wars that are now taking place will have a tendency, in some measure, to open the way for the Elders of the Church of Jesus Christ to go and establish the Church and kingdom of God among those nations.