[Kuruharan]

What was the nature of Dwarves that fell into evil? In what way were they evil?

It is indisputable that Tolkien said some of them did. These references range from the simple to the relatively complex and informative (or not so informative, depending on your perspective).

On the simple end we have…

…in some parts wicked dwarves had even made alliances with [goblins].
-Over Hill and Under Hill

and

Of the Dwarves few fought upon either side; but the kindred of Durin of Moria fought against Sauron.
-Of the Rings of Power and the Third Age

...clearly implying that some did fight for Sauron.

There is also note 28 in Of Dwarves and Men, referring to the suspicion that early tribes of Men held of the Longbeards…

For they had met some far to the East who were of evil mind. [This was a later penciled note. On the previous page of the typescript my father wrote at the same time, without indication of its reference to the text but perhaps arising from the mention (p. 301) of the awakening of the eastern kindreds of the Dwarves: “Alas, it seems probable that (as Men did later) the Dwarves of the far eastern mansions (and some of the nearer ones?) came under the Shadow of Morgoth and turned to evil.”]

This passage indicates that this corruption of the Blacklocks and Stonefoots (and potentially of the Ironfists and Stiffbeards) must have happened fairly soon after those Houses left Khazad-dum and returned to the places where their Fathers awakened.

Clearly something happened to at least some of the Dwarves. However, the nature of…whatever this was…is rather ambiguous.

We have a simple statement from Tolkien that…

[Dwarves] are not naturally evil, not necessarily hostile
-Letter 156

…so there is nothing inherently evil about Dwarves. Something must have corrupted them. Obviously, this would be the influence of Melkor. The timeline for this is a bit…difficult and it is not my intention to explore that here (at least in this post). However, the ambiguous aspect of this Dwarven descent into evil is that these evil Dwarves apparently still had normal, peaceful, and even cooperative contact with their non-evil kin in the West.

Though these four points [ancestral halls of the Seven Houses] were far sundered the Dwarves of different kindreds were in communication, and in the early ages often held assemblies of delegates at Mount Gundabad. In times of great need even the most distant would send help to any of their people; as was the case in the great War against the Orks (Third Age 2793 to 2799).
-Of Dwarves and Men

and

Durin’s Folk gathered all their host, and they were joined by great forces sent from the Houses of other Fathers; for this dishonour to the heir of the Eldest of their race filled them with wrath.
-Durin’s Folk, Appendix A

and

He is an enemy quite beyond the powers of all the dwarves put together, if they could all be collected again from the four corners of the world.
-An Unexpected Party (emphasis mine)

So these good and evil dwarves could and did work together…ironically enough at least once to fight against evil creatures that were the primary servants of someone who at least had some influence over some of them. That the evil dwarves would fight orcs is not itself surprising as Tolkien never depicted cooperation as being one of the evil side’s strong points. However, the motivation of the evil Dwarves to fight is interesting. They fought out of a sense of shame and dishonor and to help their kin. These are not impulses one tends to associate with evil creatures.

Also, note that the great conclaves of the Dwarves that took place at Mount Gundabad happened in the early ages at approximately the same time that early Men were having problems with evil Dwarves in the East. Did the good Dwarves not know what had happened, did the evil Dwarves lie to them, or did the good Dwarves not really care that much?

Ah-ha! you say. There is this quote…

A warlike race of old were all the Naugrim, and they would fight fiercely against whomsoever aggrieved them: servants of Melkor, or Eldar, or Avari, or wild beasts, or not seldom their own kin, Dwarves of other mansions and lordships.”
-Of the Sindar (emphasis mine)

…perhaps the good Dwarves and the evil Dwarves didn’t get along too well after all. However, warfare amongst the Dwarven Houses after the very early period when they were all together would have been, in many ways, a rather impractical affair. The early stage warfare that may or may not have taken place when all Seven Houses were together in the Misty Mountains would have been before the Eastern Houses fell into evil. After Dwarven civilization split up and went its separate ways it would have been difficult (to put it mildly) for the “good” Western Houses to go fight the “evil” Eastern Houses. First of all, just getting there would have been almost impossibly difficult. Then after they got there, what were they supposed to do except just burn and kill everything in sight (which would not have been very easy anyway) and then turn around and leave? It just does not seem very practical or useful. I don’t think that we can say that one Dwarf House fought another because they thought their opponent was “good” or “evil” with one exception…the War of the Last Alliance. Tolkien said that Dwarves fought there for Sauron and that the Longbeards fought for the Last Alliance. The extent of participation for both groups is cloudy at best. The reason why the Longbeards fought was basically because they were “good,” although by this point they had plenty of reason to want Sauron gone for purely practical reasons as well. Why the “evil” Dwarves fought is actually not as clear. “It is because they were evil,” is the obvious answer, but I think that is only a partial explanation. Tolkien repeatedly described Dwarves as being resistant to any form of outside domination. Indeed, their resistance to domination is the reason Sauron hated them in general and the Longbeards in particular. I don’t think the evil Dwarves fought against the Last Alliance because they had to.

What I think other inter-Dwarven warfare could be referring to I’ll save for my fourth arcane topic.

Back to the subject at hand, I think that the above reference to Dwarven resistance to domination may hold an oblique clue as to the nature of a bad Dwarf’s “evil”.

The only power over them that the Rings wielded was to inflame their hearts with a greed of gold and precious things, so that if they lacked them all other good things seemed profitless, and they were filled with wrath and desire for vengeance on all those who deprived them.
-Durin's Folk, Appendix A

This was the effect the Dwarven Rings had on those who possessed them. I think this may have been the effect that the power of Melkor had over the Eastern Houses and this was the nature of Dwarven evil (or at least the heart of it). Morgoth’s power took the gold-lust and possessiveness that was in the heart of even a good dwarf and inflamed it beyond all reason. This seems in keeping with Morgoth’s M.O. in taking a thing and warping it so that a comparatively benign trait becomes depraved. (Okay, so gold-lust, etc. might not be exactly “benign”, but you get my point.) An interesting note in this context is that Tolkien said the element Morgoth had the greatest influence upon was gold.

For the form Dwarven evil took and why Men might have had bad experiences with Dwarves in the East, I think a comparison with the Western Dwarves might be useful. The system the Western Dwarves developed and used in the First and Second Ages was one of exchange and more than a little of what might be called “patronage.” The Dwarves provided goods and built for Men. In exchange, Men revered the Dwarves (particularly in the early days), grew food for them, did other things the Dwarves didn’t want to do, and fought wars for them. The Longbeards employed this system, particularly in the Second Age, with great success. It is reasonable to suppose that they used it in some form in the First Age and the Firebeards and Broadbeams employed it as well, especially on the eastern side of the Blue Mountains away from the influence of those pesky Elves. However, it doesn’t take a great deal of imagination to see how this system might be employed by somebody of a greedy, possessive, and, well, “evil” bent. Rather than cooperation, the Eastern Dwarves might have had something more akin to domination in mind. They probably viewed early Man with a similar eye to the Western Dwarves, but instead of cooperating with Men, they could well have tried coercion to get what they wanted. Attempts by the Eastern Dwarves to enslave Men are probably not out of the question. Indeed, this theory could be easily used to explain why wicked Dwarves would have made alliances with orcs. They both wanted slaves and humans provided a ready source of mutually agreeable material. (Although, if the Eastern Dwarves were willing to enslave humans, there is little reason to suppose they’d refrain from enslaving orcs too if they could. Dwarves and Orcs are generally described as being hostile toward one another across the board. And for those of you who remember the “Elves eating Petty-Dwarves” business, here’s your revenge…the Eastern Dwarves probably would have enslaved any Avari they came across as well. In fact, they would have been ideal material for it, slaves that didn’t die…easily.)

This could explain why all the Dwarves could have still worked together. Early on, the behavioral differences of the different Dwarf Houses could have been seen as more a matter of degree than intent. However, as time passed, the Houses did grow more distant from each other and perceptions of good and evil on the other’s part may have had something to do with it. But even late in the Third Age (after the Last Alliance) they were all still able to work together so the Dwarves may not have viewed these matters in the same way as one might think they should.

There is also another source to inform a view of how the evil Dwarves could have behaved…

…the Nauglath in those days did great traffic with the free Noldoi, and, ‘tis said, with the Orcs and soldiers of Melko also.

and

Moreover [Naugladur] gathered about him a great host of the Orcs, and wandering goblins, promising them a good wage, and the pleasure of their Master moreover, and a rich booty at the end; and all these he armed with his own weapons.
-The Nauglafring

…Tolkien’s earliest conception of amoral Dwarves who were willing to deal with anybody who could profit them and use whatever means to get what they wanted.

I think the reason why some of the evil Dwarves fought for Sauron at Dagorlad was probably because he hired them as mercenaries.

Admittedly, these theories are based on supposition, but I think it is supposition based on the texts and does answer some of the questions posed by the issue.