Alma 53:6

And it came to pass that Moroni had thus gained a victory over one of the greatest of the armies of the Lamanites, and had obtained possession of the city Mulek, which was one of the strongest holds of the Lamanites in the land of Nephi; and thus he had also built a strong hold to retain his prisoners.

Moroni won a victory over one of the biggest Lamanite armies. He took control of the city of Mulek. It was one of the strongest Lamanite places in the land of Nephi. He also built a strong place to keep his prisoners.

Through all this, Moroni had won a victory over one of the greatest Lamanite armies and captured Mulek, one of their strongest fortresses in Nephite territory. And now he’d built a secure prison to hold his captives.