the definative balrog answer :)

[Galin]

I'm not sure the battle with Glorfindel is much described even in short prose versions after Tolkien had written the encounter in Moria, or finished The Lord of the Rings. Here's what I could find anyway, in the very late (early 1970s) essay on Glorfindel (Last Writings):

'... who in the pass of Cristhorn ('Eagle-cleft') fought with a demon, whom he slew at the cost of his own life.'

'... had sacrrificed his life in defending the fugitives from the wreck of Gondolin against a Demon out of Thangorodrim*

*in the margin Tolkien wrote: 'The duel of Glorfindel and the Demon may need revision'

In the first example the word 'Balrog' was changed to demon for some reason, and then Tolkien uses demon throughout (incidentally because of this I have seen at least one person argue the possibility that Tolkien was thinking of having Glorfindel defeat a great 'demon', but maybe not a Balrog necessarily). Anyway, it is somewhat amusing (to me) that Tolkien wrote 'may need revision' since the last time he had described this battle in any real detail was how many years ago? The quotes above were written no earlier than 1970, and the version of The Fall of Gondolin given in The Book of Lost Tales is that of 'Tuor B' in its final form, before Tolkien read the story at Exeter College in 1920. Going by that alone we have 50 years!

In the detailed long prose version Glorfindel was arguably battling an 'old conception Balrog'. If Tolkien had decided to give Balrogs wings only by the ultimate draft of The Lord of the Rings, then as the former encounter stood, Glorfindel's Balrog had no wings and could not fly in any case. I'm not trying to raise a side discussion on whether or not pre-Lord of the Rings Balrogs had wings or could fly, but for myself I think the evidence is fairly strong that they could not. To give one citation (and I think it is safe to say that in the late 1930s the Balrogs were not yet Maiar), in the Quenta Silmarillion written at this time it was said: 'But he loosed upon his foes the last desperate assault that he had prepared, and out of the pits of Angband there issued the winged dragons, that had not before been seen; for until that day no creatures of his cruel thought had yet assailed the air.'

Back to the texts: from the Later Annals of Beleriand (mid 1930s): 'They fell into ambush there, and Glorfindel of the house of the Golden Flower of Gondolin was slain, but they were saved by Thorndor, and escaped at last into the vale of Sirion.' I had to go back to 1930 (The Quenta) to find text that even describes the matter in enough detail to state they both fell: 'Songs have been sung of the duel of Glorfindel with the Balrog upon a pinnacle of rock in that high place; and both fell to ruin in the abyss.' In any case obviously Tolkien in 1972 could have retained the same basic story as back in 1920 and 1930. It's in his head still, if not again on paper. All I am saying is that as far as actual written text goes, he had only described this battle in any real detail very early, and had then only briefly referred to it before he wrote the encounter in Moria; and only briefly referred to it after the encounter (though I didn't check my linguistic documents here, I should add).

OK, so what about this possible revision? if the Balrog of Gondolin was 'now' a Balrog or 'Demon of might' as in one of the Maiar taken demon form, and if Tolkien now also imagined Balrogs could fly, where before they could not, then JRRT noting to himself this duel 'may need revision' arguably might go well beyond altering the archaic style he had employed back in his youth. And such beings could arguably, at least, now take on even the Eagles of Manwe (at least some of them), even if only at most seven (referring to the marginal note in AAm) ever existed. And the walls of Gondolin would now not be high enough for them, once the city was attacked.

And if so, where before he had held the winged dragons until the very end, now Tolkien would be introducing powerful flying Maiar into the picture very early with respect to the history of Beleriand (and these would be relatively huge beings too, for people who agree with Jackson's version)?

Hmmm

For myself I think 'old Balrogs' had no wings and couldn't fly, and I don't think JRRT gave his 'new Balrogs' flight or actual wings (nor do I think the thing changed shape in The Lord of the Rings after it fell into the water). What I think Tolkien did do was add terror by obscuring the form of the Demon. In the drafts of the Moria encounter CJRT notes that the Balrog could be clearly seen. However Tolkien then noted to himself...

'Alter description of Balrog. It seemed to be of man's shape, but its form could not be plainly discerned. It felt larger than it looked'. After the words 'Through the air it sprang over the fiery fissure' my father aded 'and a great shadow seemed to black out the light.'

The Bridge, The Treason of Isengard

I think this is one of the main moments of change in external Balrog history, along with making them Maiar and possibly drastically reducing their numbers.

Tolkien obscured it with shadow, and not a shadow as in 'lack of light' but ultimately with its own cloak of darkness, with a '... Dark which seems not lack but a thing of its own: for it was indeed made by malice out of light, and it had the power to pierce the eye, and to enter heart and mind, and strangle the vey will.' The Annals of Aman

Ok that description concerns Ungoliante actually some kind of living shadow like that then. Which at one point in Moria, looked like wings.