While Ammon may have been confident in the protection of the Lord, he began his defense from a distance. Using a sling he cast stones at his enemy and killed six of them (see verse 38). During this time, the other group also began to sling stones, though their aim was not as sure as Ammon. When they were unable to subdue Ammon from a distance, they "came forth" with their clubs.
Stones are effective from some distance, but closing the distance to a personal contact makes the stones ineffective. At close range, the men choose their "clubs." We will discuss the weaponry in the next verse. In this case, the combative situation has begun with several men against one at a distance, and now will consistent of multiple men against one in close combat.