Alma 52:26

And thus Moroni had obtained a possession of the city Mulek, with a part of his army, while he marched with the remainder to meet the Lamanites, when they should return from the pursuit of Teancum.

Moroni took control of the city Mulek with part of his army. He marched with the rest of his men to meet the Lamanites when they came back from chasing Teancum.

So Moroni captured the city of Mulek with part of his army, while he marched with the rest to meet the Lamanites when they returned from chasing Teancum.