Alma 2:13

and thus they were prepared to meet the Amlicites at the time of their coming. And there was appointed captains, and higher captains, and chief captains, according to their numbers.

They were ready when the Amlicites came. They picked captains and higher captains and chief captains based on how many people they had.

They organized themselves under captains, senior captains, and chief captains, ready to meet the Amlicites when they came.