Alma 43:31

Therefore he divided his army, and brought a part over into the valley, and concealed them on the east, and on the south of the hill Riplah;

So he split his army into two parts. He brought one part into the valley and hid them on the east and south of the hill Riplah.

He divided his army and brought part of it into the valley, hiding them on the east and south sides of the hill Riplah.