I recently found out about the war of Arnor vs Angmar, and was pretty shocked to learn that the Witch King basically wiped the floor with the dúnedain kingdom... I mean he's basically the sole reason Aragorn wonders around like a homeless person.

So what I would like to know is with what army did the Witch King defeat Arnor? Orcs? Men? Sorcery? did he ever go to battle himself? did he do this for laughs or by Sauron's orders?

How powerful was the Witch-King at this point, compared to in the Fellowship of the ring and Return of the king? were the others Nazgul with him in this war?

And it doesn't even matter to me if all of the 8 nazul were with him, even if they all had their rings of power, and even if they had the largest of armies of orcs, men, elves, dwarves or even dragons (yes I'm exaggerating at this point), but just how the hell do you defeat a kingdom full of Dúnedain? I mean we have all seen what Aragorn is capable of doing, so how do you defeat a kingdom worth of Aragorns?

And if it is not much to ask, does anyone know where I can read all about this war and more about the Witch-King? so far all I read about it was from the internet, wikis, forums and alike, I'd like to read if from the source