[rutslegolas]

i think that the oliphaunts are really good for fighting against foot soldiers(infantry)

and they could easilt trample over a "eored"
of horses of rohan in close formation

or they could just trample the knights of gondor

and on the oliphaunts there were siege towers or catapults which they could use to launch an assault over the walls of minas tirth

so i guess they were really important in the battle