The combat is a complete rout of the Lamanite army (at least as told by the Nephites). Even though the Lamanite army must have been sizeable to have wreaked such destruction on Ammonihah, the battle, the forced march over difficult terrain, and managing both booty and captives must have been fatiguing. In contrast, Zoram’s troops would have been much fresher and unwearied by combat. They also traveled a shorter distance over presumably easier terrain. It seems reasonable to assume that they used what must have been a relatively well-traveled road between Zarahemla and Manti.
The comment that the captives were “brought by their brethren to possess their own lands” is ambiguous. To whom did the “own lands” originally belong, the Ammonihahite prisoners or the Zarahemlaites? This ambiguity is cleared up in verse 11, which makes it clear that no one settled again in Ammonihah. Therefore, the released prisoners received new lands elsewhere in the polity of Zarahemla.