Did Sauron suspect that the Ring would be destroyed?

Question

In The Lord of the Rings, the strategy is to infiltrate the One Ring into Mordor undetected and destroy it in Mount Doom.

However in "The Choices of Master Samwise", Shagrat and Gorbag have this conversation :

..."About an hour ago, just before you saw us. A message came: Nazgûl uneasy. Spies feared on Stairs. Double vigilance. Patrol to head of Stairs. I came at once."

Then later, they relate these orders that come from Lugbúrz (Barad-dûr) -

"Any trespasser found by the guard is to be held at the tower. Prisoner is to be stripped. Full description of every article, garment, weapon, letter, ring or trinket is to be sent to Lugbúrz at once and to Lugbúrz only. The prisoner is to be kept safe... until He sends or comes Himself".

The "He" here is clearly Sauron.

Does this imply Sauron had a suspicion the Ring was being smuggled in?

Answer 1

Sauron is not stupid! But he--like all of us--is limited by his picture of what the world is like:

[H]e is very wise, and weighs all things to a nicety in the scales of his malice. But the only measure that he knows is desire, desire for power; and so he judges all hearts. Into his heart the thought will not enter that any will refuse it, that having the Ring we may seek to destroy it. If we seek this, we shall put him out of reckoning.'

Like anyone with more problems than resources to deal with them, planning is a matter of cost/benefit.

Sauron judges (for good, though incorrect, reason) that the chance of someone trying to destroy the Ring is negligible.

The Enemy, of course, has long known that the Ring is abroad, and that it is borne by a hobbit. He knows now the number of our Company that set out from Rivendell, and the kind of each of us. But he does not yet perceive our purpose clearly. He supposes that we were all going to Minas Tirith; for that is what he would himself have done in our place. And according to his wisdom it would have been a heavy stroke against his power. Indeed he is in great fear, not knowing what mighty one may suddenly appear, wielding the Ring, and assailing him with war, seeking to cast him down and take his place. That we should wish to cast him down and have no one in his place is not a thought that occurs to his mind. That we should try to destroy the Ring itself has not yet entered into his darkest dream.

So what should he do to deal with this highly unlikely case? Station guards all around Mt. Doom? No. This is very expensive (not only do you spend the guards, but you also need to supply them with food and water in a foodless and waterless wilderness). Big cost, low return.

But he knows that the Ring is at its most powerful at Mt. Doom and probably gains in power as you approach the mountain. It's a long shot, but maybe, just maybe, when Aragorn (or Boromir or whoever) takes the Ring for himself, A. or B. or W. will head off to Mt. Doom to launch his challenge of Sauron. Still too much of a long shot to warrant stationing an army around Mt. Doom, but it is worthwhile to alert the border guards -- which he needs anyway -- with orders to properly handle any Ringbearers they might capture. That's very low cost and is a sensible precaution against a low-probability event.

If Sauron had suspected that there was any chance at all that the Ring might be destroyed -- literally the most catastrophic possible event from his point of view -- then that chance would be enough to justify guards all around Mt. Doom.

Sauron is a rationalist, a techie, a hard-headed believer that good planning and self-interest is the best way forward--and he thinks everyone else is that way too and that he understands them. Again, I emphasize, he is not stupid and "all things [are weighed] to a nicety in the scales of his malice."

So, no guards ⇒ no suspicion.

Answer 2

In addition to Marks' answer, it's worth pointing out that he might not have been referring to the actual One Ring. We know there are other rings; the Three, for example, or even one of the "lesser rings" that Gandalf describes as "essays in the craft before it was fully-grown".

Answer 3

Mark Olson gives the evidence we have in an excellent answer. It’s important to recall, however, that those statements are Gandalf’s supposition about what Sauron would do.

While wise, Gandalf is not omniscient. We also have reason to doubt how well Gandalf truly knows Sauron. There is no indication that the two of them have ever so much as met. If so, it must have been longer ago than Saruman changed without Gandalf’s knowledge, causing him to drastically misjudge Saruman. Sauron certainly never confided to Gandalf, or to anyone who told Gandalf, what his strategic analysis was. So, it is plausible that Gandalf is overestimating how perfect his own plan is—or possibly even telling the Hobbits a little white lie, in order to keep their spirits up.

However, he might not need to rely on his own knowledge of Sauron. Galadriel tells Frodo (it is not clear how figuratively or literally, but at the very least she has learned a great deal of military intelligence through her mirror):

I say to you, Frodo, that even as I speak to you, I perceive the Dark Lord and know his mind, or all of his mind that concerns the Elves.

He could well have found out from her.

Our most direct evidence is what Sauron’s own actions reveal about his planning. We do know that Sauron fell for the Fellowship’s ruse and believed Aragorn had the One Ring, therefore leaving Mount Doom unguarded. Thus, his forces would otherwise have been guarding the approach to Mount Doom (but possibly for other reasons, such as logistics). And, as you mention, we know that he told his troops to be on the lookout for someone trying to smuggle a ring into Mordor. Therefore, it had at least occurred to him as a possibility that someone would take the Ring to Mount Doom. He acts as if he believes that Aragorn, like his ancestor he was emulating in every other way, will invade Mordor to fight him at Mount Doom and seize his throne, and as if he assumed that the One Ring would never allow its bearer to destroy it.

Answer 4

Sauron might suspect an assassination attempt

It would have been really hard to get a whole army inside Mordor, even with the help of the Ring, because Mordor had a larger army and formidable fortifications. What would Sauron have done then if he had been in Gandalf's place?

A smaller commando or even a single powerful actor, like Gandalf, Galadriel or what remains of that ragtag Rivendell fellowship, empowered by the Ring, could infiltrate Mordor with the goal of killing him. Maybe such a ringbearer would even have the power to collapse Barad-dûr itself, since its foundations relied on the power of the Ring.

That is a practical, sensible plan that would put the ringbearer in a position of power. It fits in with Sauron's worldview, so he's "capable" of thinking about it and making plans to protect from it.

In this case there's no need to guard Mt. Doom. Barad-dûr, on the other hand, would need some tight security, but it's probably already in place anyway.