The problem with war is it arouses the instinct for killing. As men adapt to war, they become predatory, seeking to destroy those they view as the enemy. They study and train to trade life for death.
Zion will not possess those skills. They won't learn them and will not need them. Zion will be a place of peace, where those who are unwilling to take up arms against others will flee. (D&C 45: 66-69.) Though peaceful, the glory of the Lord will strike such fear among the wicked they will not dare come up against that place. (D&C 45: 70.) As unlikely as this seems, it is true.
When mankind has degenerated to the point of looking at one another as prey, the Lord will not allow His people to become prey to the terrible and the mighty. As Jacob (borrowing from Isaiah) explained, "For shall the prey be taken from the mighty, or the lawful captive delivered? But thus saith the Lord: Even the captives of the mighty shall be taken away, and the prey of the terrible shall be delivered; for the Mighty God shall deliver his covenant people. For thus saith the Lord: I will contend with them that contend with thee." (2 Ne. 6: 16-17. ) The Lord intends to establish His covenant among those who take the Spirit as their guide, who reject the doctrines of men as truth, who do not trust in the arm of flesh, and who have not dwindled in unbelief.
Those who qualify, and who are in a covenant with Him, will see the destruction of those oppressors who threaten them. The armies and mobs who think they can overtake Zion will learn to their dismay that the Lord intends to protect them in such unmistakable acts they will be compelled to confess He is God and Zion is His people. As Jacob put it: "And I will feed them that oppress thee, with their own flesh; and they shall be drunken with their own blood as with sweet wine; and all flesh shall know that I the Lord am thy Savior and thy Redeemer, the Mighty One of Jacob." (2 Ne. 6: 18.)
The Lord has two contradictory persona's in scripture. He is the Lamb of God, and He is the Lion of Judah. Those two persona's appear in widely separated passages of scripture. They merge together in one passage of scripture written by the Apostle John. It was John who shared Nephi's vision and who was permitted to write of it. Nephi deferred to him. John uses both titles in succession when describing the Lord's role in loosing the seven seals, calling the Lord both "the Lion of the Tribe of Judah" and "a Lamb as it had been slain." (See Rev. 5: 5-6.) He is the Lion of Judah to those who seek to prey upon His covenant people. He is the Lamb of God to His own.
When you see the Lamb and the Lion lie down together, you may know the Day of Judgment is at hand. It will be both great and terrible to the righteous and wicked.
Jacob knew this. Jacob saw these things before they happened, so he could write his testimony as a warning to those who live in the last days. He was a prophet more for our day than for his own. Provided, of course, we have the eyes and faith to see it.
Jacob's skill in expounding doctrine is not limited to his commentary. It includes the careful selections from Isaiah chosen to illustrate his points and clarify his views. Since he saw the Lord and was ministered to by Him, Jacob becomes adept in recognizing and expounding truth in a way which is trustworthy, and reflects his knowledge of the Lord's great work to save the souls of men.