In the Third Age of the Sun in the south lands of Harad, there lived beasts of vast bulk that are thought to be ancestors of the creatures Men now name Elephants. Yet it is said the Elephants that now inhabit the World are much smaller in size and might than their ancestors.
In the years of the War of the Ring the fierce warriors of Harad came north to the lands of Gondor at the call of Sauron, and with their armies they brought the great Mūmakil, which were used as beasts of war. The Mūmakil were harnessed with the gear of war: red banners, bands and trappings of gold and brass; on their backs they had great towers from which archers and spearmen fought. They had a natural thirst for battle, and many foes were crushed beneath their feet. With their trunks they struck down many enemies and in battle their tusks were crimsoned with the blood of their foes. They could not be fought by mounted Men, for Horses would not come near the Mūmakil; nor by foot soldiers, who would be shot from above or crushed. In war they would frequently stand as towers that could not be captured: shield-walls broke before them and armies were routed.
These thick-skinned beasts were almost invulnerable to arrow-shot. In only one place, their eyes, could the Mūmakil be blinded or even killed by arrows released with great force. When blinded they became enraged with pain, and often destroyed masters and foes alike.
see also: Oliphaunts