Helaman 4:8

And thus those dissenters of the Nephites, with the help of a numerous army of the Lamanites, had obtained all the possession of the Nephites which was in the land southward. And all this was done in the fifty and eighth and ninth years of the reign of the Judges.

So the Nephites who left, with help from a huge Lamanite army, had taken all the Nephite lands in the south. All this happened in the fifty-eighth and fifty-ninth years of the judges’ rule.

And so these Nephite traitors, backed by a massive Lamanite army, captured all the Nephite lands in the south. All of this happened in the fifty-eighth and fifty-ninth years.