Why not march over Rivendell and take the ring?

Question

After the battle on Weathertop the Nazgûl learn Frodo has the one ring and follow him to Rivendell, where Glorfindel defeats them.

They have however by that time acquired the knowledge about the one ring's location. Why didn’t Sauron march his troops over to Rivendell and simply take it?

And if the answer is, he didn’t have enough troops / power, why didn’t the reverse happen, with elves, Rohan and Gondor joining forces to attack Mordor? And if the answer to that is they weren’t allies anymore, then what would have prevented Sauron from attacking then?

Note Similar but not equal to Did Sauron have the military power to control all Middle-earth? as that one talks about needing the ring to take over “all middle earth”. While Sauron doesn’t have enough power to do that, this is more of a focused attack on Rivendell to get the one ring

Answer 1

I don't think we can give a definitive answer, because Tolkien never did, but a pretty clear answer can be worked out.

First, it's clear that Rivendell had substantial powers of resistance -- doubtless due in large part from Elrond's Ring. It's impossible to imagine that over thousands of years the Orcs never discovered its location, so they knew of it, but didn't dare attack (or attacked and were repulsed.) So Rivendell may have been a homely house with restful scenery and good food, but it was also a formidable fortress. The nearby orcs -- even if they chose to follow Sauron's orders -- could not have taken Rivendell.

Second. Take the Ring with Orcs? "How very trusting you have become in your old age, Mr. Sauron." The only entities Sauron could trust to take the Ring were ones he utterly dominated. So the only local forces were untrustworthy and couldn't be used even if they had the power to take Rivendell.

Third, So he had to bring up forces from Mordor. But logistics. By the time Sauron knew the Ring was in Rivendell, the Fellowship had left or was about ready to leave. There simply was no time to move trustworthy resources that far. (See What's the big deal about the Nazgûl losing their horses? for some discussion on timing.)

(This is a bit of a weak spot, since while there was insufficient time in 'reality', how could Sauron have known that? If he expected the Ring to go to earth in Rivendell, then he should have started a mobilization to send forces that he dominated north to get it. But apparently he didn't.)

Fourth, as @Valorum noted, it's much harder to take a fortress than to defend it. Elrond knew that he lacked to power to attack -- and in fact, he knew that he lacked the power to defend Rivendell indefinitely against Sauron.

... have we here the strength to withstand the Enemy, the coming of Sauron at the last, when all else is overthrown?'

'I have not the strength,' said Elrond; 'neither have they [referring to the just-mentioned Cirdan, and the rulers of Lórien]'

Bottom line: There was no practical way for Sauron to take the Ring by forces before it left Rivendell, and Elrond did not have to force to take on Sauron.

Answer 2

In addition to Mark Olson's great answers, there are two other factors.

1. Gondor is still a military threat to Mordor - a premature attack on Rivendell opens an opportunity for Gondor to attack Mordor. If the attack on Rivendell fails, Sauron is now in a much worse position, which ties into 2.

2. If the Ring is unavailable, Sauron will eventually be able to dominate Middle-Earth - but if the Ring is at Rivendell, Sauron must fear that someone intends to use it, and Gandalf, at least, is someone who could use the Ring to overthrow Sauron. Sauron must take that possibility into account (and in his mind, that is a much more likely thing to be happening than a council of the mighty deciding to try to destroy the Ring). Marching on Rivendell might be what Gandalf wants Sauron to do. Better to control and expand his realm in Mordor and its environs than to take the chance.

Note: In response to the comment below from Gallifreyan: "Corruption" is an ambiguous word. Given enough time, the less-powerful (Hobbits, dwarves, most or all men, most or all elves) will be corrupted by the Ring into tools of Sauron, who would turn the Ring over to him and serve him (we see a shadow of that in the relationship between Gollum and Frodo). The truly powerful, however, might master the Ring - they will still be corrupted into becoming devoted only to power, and having all their good goals twisted into evil - but they would retain enough will to overthrow Sauron. Sauron gets no pleasure out of the fact that his defeater would be corrupted in that sense - Sauron himself would be destroyed (or turned into a servant). I don't know if Aragorn or Elrond has enough power to master the Ring (note that the Ring tries to convince people that mastering it is possible even for people like Samwise for whom it is not possible, as a means of corrupting in the other sense), but Gandalf, a Maia, is certainly someone who could, if he chose, master the Ring, and thus is a mortal threat to Sauron.

Answer 3

Why didn't Sauron march his troops over to Rivendell and simply take the ring? Because he couldn't.

It's about 900 miles from the Gates of Mordor to Rivendell. An army on the march, facing no opposition, can cover about ten miles per day*. If Sauron somehow had an army ready to depart on October 20, the day the Ringwraiths were defeated, that army could arrive at Rivendell no earlier than January 17, 23 days after Frodo departed.

But that assumption of "facing no opposition" is wrong. This is taking place in late fall and early winter. The northern route, going over the Misty Mountains at Redhorn Pass or the pass Thorin's company took, is blocked by snow. The middle route, going through the Gap of Rohan, involves fighting a protracted campaign against Rohan (you don't want to leave a hostile cavalry force as good as Rohan's in your rear). The southern route goes through the heart of Gondor, and results in combat very similar to what actually happened in the books.

Between weather, terrain, and opposition, it's unlikely that Sauron could begin an attack on Rivendell earlier than mid-June. In the actual timeline, the Ring was destroyed well before then, on March 25.

^{*A raiding force can move much faster, but a raiding force is exactly what Glorfindel just destroyed.}

Answer 4

He apparently lacked the strength.

'The the Nine had indeed arisen I felt assured, apart from the words of Saruman which might be lies. Long ere I came to Isengard I had heard tidings by the way that could not be mistaken. Fear was ever in my heart for my friends in the Shire; but still I had some hope. I hoped that Frodo had set forth at once, as my letter had urged, and that he had reached Rivendell before the deadly pursuit began. And both my fear and my hope proved ill-founded. For my hope was founded on a fat man in Bree; and my fear was founded on the cunning of Sauron. But fat men who sell ale have many calls to answer; and the power of Sauron is still less than fear makes it. But in the circle of Isengard, trapped and alone, it was not easy to think that the hunters before whom all have fled or fallen would falter in the Shire far away.'

-- Gandalf, The Council of Elrond (emphasis mine)

As for why not march over and attack Mordor then - supply lines come to mind. Marching an army across a continent is not something easily done, and the further away you are from your home base the harder it gets to keep them supplied. This applies to modern armies, and presumably also to Tolkien's armies.

One more thing comes to mind: it's said that Saruman might have been able to resist the Nine even after Gandalf shattered his staff, as long as he remained in the Orthanc. If something applies to Sauron & Barad-Dur, attacking Mordor might not be wise even if it's practical.

Answer 5

Don't forget that Rivendell was hard to find even if you knew where it was. From The Hobbit:

It was indeed a much wider land from the ford to the mountains than ever you would have guessed. Bilbo was astonished. The only path was marked with white stones some of which were small, and others were half covered with moss or heather. Altogether it was a very slow business following the track, even guided by Gandalf, who seemed to know his way about pretty well.

His head and beard wagged this way and that as he looked for the stones, and they followed his lead, but they seemed no nearer to the end of the search when the day began to fail. Tea-time had long gone by, and it seemed supper-time would soon do the same. There were moths fluttering about, and the light became very dim, for the moon had not risen. Bilbo’s pony began to stumble over roots and stones. They came to the edge of a steep fall in the ground so suddenly that Gandalf's horse nearly slipped down the slope.

It's possible Elrond's Ring also helped keep the valley hidden. I suspect no orcs or goblins ever found the valley, and if they did they didn't live long enough to report it to anyone.