The film can be criticized for omitting a large portion of
Moore's book. The film depicts only the first half of the Battle of
Ia Drang, which took place at Landing Zone X-Ray, and shows Moore's
successful defeat of a North Vietnamese attack. It does not depict
the second half of the battle: after Moore's troops had left the
Landing Zone, the men from Company C, who had arrived to support
Moore's troops, were left to march to Landing Zone Albany. Colonel
McDade, the leader of these troops, made a tactical mistake on the
trail, calling forward all of his commanders to interrogate two
unarmed North Vietnamese soldiers. A sudden ambush cut off platoons
from their officers, and the American Troops suffered many
casualties. By omitting this part of the battle, the movie suggests
that it was an unambiguous victory, when in fact Moore himself
considers it to have been a draw.
Source: Wikipedia