

Indeed, Uruk-hai frequently displayed total contempt towards their lesser cousins, even killing and devouring them on at least one occasion.

The Uruk-hai were clearly meant to be the super-soldiers to the armies of evil, also likely meant to ultimately replace the inferior Orcs altogether. There are suggestions that the Uruk-hai created by the fallen wizard was the result of crossbreeding Orcs with Men or with Goblin-men. The Uruk-hai were created by Sauron late in the Third Age.
