It's not just about having the power...

[Ibrîniðilpathânezel]

I was able to get at one of the bookshelves in my office (after it's cleared out, I think I'm going to call it my studio ), and Morgoth's Ring was on the shelf. The passage I have in mind is in an appendix to the Athrabeth, concerning a conversation between Eru and Manwë and the matter of the reincarnation of Elves who have died:

There were many such fëar of Elves who had died in Middle-earth gathered in the Halls of Mandos, but it was not until the death of Míriel in Aman that Manwë appealed directly to Eru for counsel. Eru ‘accepted and ratified the position’ — though making it plain to Manwë that the Valar should have contested Melkor’s domination of Middle-earth far earlier, and that they had lacked estel: they should have trusted that in a legitimate war Eru would not have permitted Melkor so greatly to damage Arda that the Children would not come, or could not inhabit it (cf, LQ 20, page 161: ‘And Manwë said to the Valar: “This is the counsel of Ilúvatar in my heart: that we should take up again the mastery of Arda, at whatsoever cost, and deliver the Quendi from the shadows of Melkor.” Then Tulkas was glad; but Aulë was grieved, and it is said that he (and others of the Valar) had before been unwilling to strive with Melkor, foreboding the hurts of the world that must come of that strife.”)

By "far earlier," it's rather plain that Eru meant before the waking of the Children ("that the Children would not come or could not inhabit it [ME]"). It appears that a majority of the Valar were not in favor of fighting Melkor out of fear that it would severely damage the world, which was a mistake on their part because they lacked estel, hope, as Eru tells them. They lacked trust and faith in him, and thus did not properly use both their might and their authority. If the Valar had done as they ought, with hope and trust that Eru would never let Melkor win the "real war"-- which was between the renegade and Eru -- then a great deal of later destruction, pain, and suffering would have been avoided. There wouldn't be the tales of valor, heroism, betrayal, and tragedy which followed, but it would have been a more peaceful world.

I'm glad I found it -- I was beginning to think I'd gone nuts.