1 Nephi chapters 1-8 are apparently an abridgment of the book of Lehi; from that point on Nephi became an author rather than an editor. The first 116 pages that Joseph Smith translated—which were subsequently lost—came from the book of Lehi. Joseph Smith was commanded not to retranslate this material (see D&C 10).
“All That Fight Against Zion Shall Be Destroyed”
Israel’s triumph over her enemies will occur not because her marching armies defeat their foes in battle, but because her enemies [the Gentiles, the great and abominable church, the nations that fight against God-call them what you will, the meaning is the same] will be destroyed, simply because every corruptible thing will be consumed at the Second Coming. In that day the Lord will truly fight the battles of his saints, for as he descends from heaven, amid fire and burning, all the proud and they that do wickedly shall be burned as stubble. (New Witness, pp. 562-63.)