The Northern Kingdoms

[Inziladun]

Originally Posted by William Cloud Hicklin

I suspect that the division of Arnor was inspired by the fate of many RW Germanic kingdoms, including Charlemagne's empire; it was a byproduct of the ultimately destructive old Teutonic custom of dividing an inheritance among the sons rather than adhering to primogeniture.

Of course Gondor was also weakened by civil war, but there it was a faction-fight over a single crown rather than armed squabbles between, say, Belfalas and Anorien.

Arnor wasn't helped by the Witch-king's appearance, either. He apparently introduced evil men into Rhudaur, and that seems to have worsened the division.
It makes one wonder that if Gondor had had an external force actively fomenting dissension, could it have avoided the fate of its northern twin?