Sauron's battle strategy

[Legate of Amon Lanc]

Originally Posted by The Might

I believe Tolkien also says something like if Sauron had attacked the elves first the Quest would never have been completed, since the Fellowship would have lacked the so needed support, not to mention since the Orcs were all coming their way...I just can't remember where he says that.

That's all from the Quest of Erebor. But of course, I think it's not necessary to point this out; if Rivendell and Lórien fell, it is obvious that the Fellowship would have had no chance. I think this is the part you are looking for:

Resistance still had somewhere where it could take counsel free from the Shadow. How could the Ringbearer have escaped, if there had been no Lórien or Rivendell? And those places might have fallen, I think, if Sauron had thrown all his power against them first, and not spent more than half of it in the assault on Gondor.

Gandalf speaks about it in conclusion with the fact that the assault of the Council on Dol Guldur, though unsuccesful (for Sauron escaped to Mordor), was still important, because if left alone, Sauron would surely soon use Dol Guldur as a base of attack against Lórien.

By the way, all these things are said by Gandalf to explain the fact why he wanted to help Thorin with his quest. He was afraid of the unguarded East, and of the Dragon, so he wanted to help to re-establish the Kingdom under the Mountain when the possibility appeared.