Invading Valinor impossible?
 

Where there any moments in the timeline of Morgoth that he could lay siege on the Undying Lands? Or is it simply beyond his power?

It was said that Morgoth's servants feared the Sea, and it's notable that neither he, nor later Sauron, ever had a navy of any sort.
In any case, I don't think it possible that he could have attacked Valinor with any hope of victory without his minions, and it's out of the question that a force that large moving toward the Helcaraxë could have escaped the notice of the Valar.

Of all his servants, only Sauron, and possibly the Balrogs and dragons, could have been any problem for the Valar at all.

I agree. I think Valinor was beyond the threat of military force; the whole continent of Aman was effectively fortified by sea and mountain. It took Morgoth hundreds of years to muster sufficient might to overmatch the Noldor and their allies at the Bragollach. I doubt he posed a military threat to Valinor. It worked much more in his favour to infiltrate the Blessed Realm as a prisoner and corrupt it from within (much as Sauron would later do with Númenor, and I can't believe I only just noticed the significance of that parallel).

Melkor was probably at the height of his powers as the Dark Lord of Utumno, in the years before the coming of the Elves and even before the founding of Valinor. At that time he was able to make an assault on the Valar, and destroy the Lamps, but even so he was still driven back and had to go into hiding in Utumno.

The Silmarillion notes:
So it seems clear that even then the Valar could have overpowered him, if they hadn't been distracted by other concerns. Subsequently there were only two main conflicts, the Sack of Utumno and the Captivity, and the War of Wrath, in both of which the Valar were victorious (it's actually doubtful if the Valar even took part in the War of Wrath).

So no, it doesn't seem likely that Melkor/Morgoth would have been able to undertake a successful attack on Valinor at all.

In the end Sauron did it with the help of the Númenorians. And doing it with an big army of Children of Ilúvatar was the one move that made the Valar hold back, I think.

As an aside thought: The idea of an Amry of Men invading Valinor was in away recurring: At the end of one version of The Book of Lost Tales their is mentioned a prophecy that such a invasion would occure after the return of Melko and that the behaviour of Men in that fight would decised the way of the end of the world.

Respectfully
Findegil

Right. The Valar were capable of dealing with Númenor, but felt they lacked the authority. They were 'governors' of Arda, but were hesitant to annihilate an entire race of people, especially one that had been given special reward for their allegiance in the past.

The lore concerning the 'end times' of Arda has always fascinated me, and that's something I really wish there was more 'canon' available for.

The Lost Tales era really envisioned an "end time" which had already occurred, and Aelwine/Eriol was to have witnessed it.

Personally I hold that the tale of Morgoth being chased up a tree and spending the rest of his days knocking down stars while Varda fixes them up behind him is 100% canon to the published Silmarillion. :D:D:D

(BoLT 2: The History of Eriol, excerpt 4. This happens before the Eriol-witnessed apocalypse WCH mentioned, because BoLT.)

hS