Words of Mormon 1:13
And it came to pass also that the armies of the Lamanites came down out of the land of Nephi, to battle against his people. But behold, king Benjamin gathered together his armies, and he did stand against them; and he did fight with the strength of his own arm, with the sword of Laban.
It's clear in the wording that the Lamanites came TO THEM to battle. And the Nephites stood against them. The Nephites did not go into their land. That follows the pattern the Lord has given for war.
So I wonder why the sword of Laban is still around. Cool artifact, but aside from that, what's the significance? Joseph Smith spoke of it as well as being one of the items he discovered along with the plates. It must mean something. As a symbol I think the sword represents quite a few things worth considering.
Here is what I found while researching. A sword was a sign of kingship. And probably God's approval of military use. Possession of it made Laban the "Captain of Fifty" in Jerusalem. When Nephi acquired it he replaced Laban as the military leader in the extended family, and he acquired kingly authority. When he later obtained possession of the brass plates, he was the "king and priest" because he possessed both symbols of authority, sword and plates. So King Benjamin being in possession of both plates and the sword of Laban made him a king and a priest. He in the first few chapters of Mosiah is able to and does lead people to Christ, they experience a spiritual rebirth. He speaks God's word with both power, and authority. So he very much is a king and a priest.
I think physical symbols or emblems of God's involvement are a sign of someone in possession of the true Gospel and are God's people. I wonder where such things are today. I hear little if anything about them. I wonder if they would be seen as superstitious instead of how such things were viewed anciently. A "prophet, priest and king" in the scriptures should possess all four things: sacred record, sacred directors, sword of authority, and urim and thummim. They are emblems. Ultimately they will belong to Christ during the Millennium.
There is a common belief that somewhere in a church vault or mountainside archives such items may be stored/hidden. When I read of these items in the past they were used, not just stored or gathering dust. So I wonder what the future will hold.