Tolkien vocabulary I (serious)

[Rimbaud]

I wouldn't characterize Gondolin as a military encampment.

Well, neither would I. In fact, I am inclined to agree with you. Yet, that wouldn't be much fun, so I'll stick to my original point and say that the 'opening of the leaguer of Gondolin' was the opening of the barracks, the armed forces spilling out, rather than the 'opening' of the City itself.

I've always thought Tolkien usually used "leaguer" to mean not so much a siege as simply a containment or partition

Absolutely. So did I, until I checked upon direction of piosennial's question. In my most recent post I found "the Siege" and "the leaguer" used interchangeably. When considered alongside the fact that "the leaguer of Angband" was not a siege insofar as we would label it - medieval siege machinery and waves of assaults - but, as you say, "a containment or partition" my thought is that perhaps Tolkien is using the word and concept "siege" in a broader sense than we would apply it today.

To dig at the etymology of "siege" itself: Middle English sege, from Old French, seat, blockade, from siegier to seat, settle, from (assumed) Vulgar Latin sedicare, from Latin sedere to sit.

Which, to my eye, does not suggest the need for any 'activity' but can indeed include "containment or partition" within its meanings.

As for my Unabridged-Oxford...sadly, currently I am bereft. He dwells in my London home and I am in exile in Philadelphia.