The word “great” here is used loosely to describe size not magnificence, as it was the slowest and least climactic battle ever fought.
The battle was so slow, in fact, that the historians even got bored and left before it was over. Thus we have no record of who won. We do know, however, that it was the only war ever fought by the sloths.
As a reminder of their brutality and show that they wont take abuse lying down (or hanging around as the case may be), the sloths began to make armor from the shells of their fallen enemies.