Alma 55:20

But he had obtained his desires; for he had armed those prisoners of the Nephites which were within the wall of the city, and had gave them power to gain possession of those parts which were within the walls;

But he got what he wanted. He had given weapons to those Nephite prisoners who were inside the city walls. He had given them power to take control of the parts inside the walls.

He’d already gotten what he wanted: the Nephite prisoners inside the city were now armed and able to take control of everything within the walls.