Running low on men

I think I’ve misunderstood before the order of operations. Ammoron offered a city to Helaman in exchange for Lamanite prisoners in the latter part of the 28th year. He then refused to exchange prisoners instead so helaman took the city without giving up any Lamanite prisoners.

I had thought Ammoron refused the exchange because Moroni had already liberated all the Nephite prisoners but I realize that is wrong because Ammoron offered morning a prisoner exchange in the beginning of the 29th year.

The fact that Ammoron twice offered deals in succession seeking the return of Lamanite prisoners suggests that he was feeling short of men to keep conducting the war.