Silmarillion - Chapter 20 - Of the Fifth Battle: Nirnaeth Arnoediad

[Formendacil]

Originally Posted by Inziladun

It doesn't bother me that they didn't find death in the battle, as I don't think that have been undesirable to them. It seems to me that they probably on the whole would have preferred that to what befell them after the Nirnaeth.

One might also say that the survival of the Sons of Fëanor was part of the general tragedy of the battle. Whether by design of Morgoth or because of their own fate brought on by the Oath, their survival of the Nirnaeth ensures that they will live to wreak havoc on Doriath and the Havens at Sirion. In fact, one might almost say that if the Sons of Fëanor had died in the Nirnaeth, that the Battle would have been far more successful, because Morgoth would have lost one of his biggest potential "assets"--namely the continued working of their Oath under the conditions of the Doom of the Noldor.

(Which is not to say that the Doom of the Noldor would have not been operative without the Oath of Fëanor, but it is clear that the Doom is at its most tragically effective whenever the Fëanorians show up.)