Why didn't Gandalf use his eagles to fly over Mount Doom and drop the ring? I know he feared what he would do if the ring overpowered him, so why not just give Frodo an eagle? And, if there would be too much risk in flying the ring to Mordor, couldn't the eagles fly them part of the way? Why risk it with such a long walk; far less risky to fly over most of the journey.
In short, the eagles would also be tempted to take the ring. At least, I've always assumed they'd rule Middle-earth with an iron talon.
Here's an excellent rundown of in-universe explanations, and a few real-world ones. It summarizes frequent Usenet discussions in rec.arts.books.tolkien of the so-called "Eagle plan" whereby the Eagles are used to fly the ring to Mount Doom. It's definitely a popular plot hole to discuss, with many pros and cons outlined there.
I think it would undermine the theme of the story, that it's about normal people taking responsibility for the world, and throwing off the dependence on ancient powers (Gandalf and Sauron included).
Also, it'd be a 10 page story.
Giant Eagles with Wizards on their back would have been seen for miles. Even a normal Elf like Legolas could spot small flying birds at some distance, the Eye of Sauron would be looking to keep his borders safe, from above and below. Sauron also had the Nazgul air force after all, and maybe others too :)
Not to mention the fact that they would have been extremely vulnerable in such a position, and likely to be brought down, and if that happened over Mordor, it would have guaranteed that Sauron got his ring back.
In terms of military strategy, it would be more of a "Hail Mary" than a solid plan, with a high risk of catastrophic failure.
With Sauron's combined forces being so strong by the time the Ring was discovered, it meant a full-on attack would be highly unlikely to succeed, and so only a covert mission would do. The point of sending Hobbits on foot was that they had showed resilience to the Ring's corrupting influence, but also that they would be unsuspected, as Hobbits were considered rather unimportant folk.
It's also worth noting that the Giant Eagles, much like the Wizards of Middle Earth, were forbidden in directly helping mortals overcoming problems they could solve themselves. They could only advise or otherwise get tangentially involved.
To sum up: The ring had to stay hidden at all times from Sauron's eye, and on top of an eagle on board up in the air would ruin the cover and could endure death.
This is not a plot hole. The Eagles are the representatives of Manwë in Middle-earth. As mentioned in the link in the accepted answer.
I am surprised that this argument comes up as often as it does, because I am aware of no textual support for this idea. The eagles quite frequently involve themselves in the fight against Sauron (or against evil in general):
They rescue Bilbo, Thorin, & Co. from the orcs and wolves. They participate in the Battle of Five Armies. They rescue Gandalf from Orthanc. They rescue Gandalf again from Zirak-Zigil. They directly attack the flying Nazgûl during the last battle. They fly into Mordor to rescue Frodo and Sam. Given all this heavy involvement, it would be extremely surprising if the Valar specifically prohibited the eagles from flying the Ringbearer into Mordor. Tolkien nowhere mentions such a prohibition.
The only support I can see for this argument is very indirect: namely, that the eagles are said to be the representatives of Manwë, and in the Third Age, Manwë is maintaining a policy of the Valar not intervening directly in the affairs of Middle-Earth. But the eagles do often intervene in the struggles of Middle-Earth, and there's no indication that they were under some restriction in this case. If the eagles were prohibited from being involved directly in the struggle against Sauron, we might expect that they would have withdrawn to Valinor long ago rather than remain in Middle-Earth.
If you look at the involvement of the Eagles it is very similar to the involvement of the Istari. The Istari are Maia sent to Middle-earth as guides and to provide some help in countering the great powers of those who had fallen. They are not allowed to solve the problems of Middle-earth, only to guide and aid those who are solving those problems. The Eagles play a similar role. Both are forces of the Valar -- who, after the first age that destroyed vast swaths of Middle-earth, vowed never again to interfere directly in the affairs of the mortals of Middle-earth -- and both aid those fighting Sauron. But only where the mortals of Middle-earth could not over come the foe on their own.
The ring is a foe that the mortals of Middle-earth could overcome. And in a way, it is the one foe they must overcome on their own. Gandalf guides them to this realization and helps them figure out the "how". But he will not defeat the foe itself.
Gandalf aids them by defeating a peer who had fallen, against which none of them could stand (the Balrog) and by helping to counter the movements of one of the Istari who had fallen. The Eagles aid them by providing some mobility and countering forces of the enemy when they take to the air, the realm of Manwë, which mortals are not truly supposed to enter.
All of these actions are consistent with the way the Valar are willing to aid those of Middle-earth. However, flying the ring bearer to Mordor is not consistent with them. That would be direct involvement and solving the one problem that those of Middle-earth need to solve themselves -- their lust for power at the expense of Middle-earth itself.
You want an "In Universe" explanation?
Because it couldn't have worked any other way.
The powers knew no one could willingly destroy the ring, therefore they needed the tussle between Frodo and Gollum, and for Gollum to fall for the ring to be destroyed.
If they'd flown on Eagles then Gollum wouldn't have been there, Frodo would have failed to destroy the ring, Sauron would have won and the fourth age would have been one of darkness across the face of Middle-earth.
There are several explanations, both in and out of universe:
- The Nazgul (more specifically their fell beasts) would have been able to take them out.
- Anything flying into Mordor, especially a rarely-seen Giant Eagle, would be quickly spotted by Sauron, who would immediately muster every force he had around and in Mount Doom. Frodo and Sam were specifically trying to avoid the Eye's gaze.
- If the Eagle (or whomever was riding it) missed dropping/throwing the Ring directly into the fires of Mount Doom, they'd be handing the Ring directly to Sauron's forces.
- Tolkien mentioned in notes and conversations that he did not want the eagles to be seen as "Middle-earth taxis". They thus intervene directly only in times of great need, as the last option.
All that plus the Eagles weren't available at the time the Ring set out on its journey from Rivendell, a journey meant to be made in secret so as to not reveal to Sauron that the Ring was on the move and to what end (to the very end Sauron was under the impression that the Ring, after having been found, would appear on the hand of one of his enemies to be wielded as a weapon of war, rather than being sent to its doom in the forges where it was created).
Sending in an Eagle bearing a Hobbit on its back, the Hobbit bearing the ring (the presence of which Sauron could detect at some distance) would have attracted too much attention, revealed to Sauron that things are not as they seem (most likely he assumed either Gandalf or the lords of Minas Tirith would unveil the Ring in the battle at the gates of Mordor).
Personally, I think something is only a plot-hole if there aren't plausible in-universe explanations, regardless of whether the author actually enumerates those explanations.
In this case, I always assumed that while there were just nine Nazgûl, there were a lot more than nine of the "fell beasts" that they flew around on--there's no indication that these creatures were made especially for the Nazgûl, or that there's some kind of limited supply of them.
Sauron raising a bunch of flying creatures in Mordor makes it a lot more risky for the Eagles to fly there, let alone to fly there with the one ring. After the ring is destroyed, though, it makes sense that the beasts' handlers have scattered and that it's safer to mount an airborne rescue mission than it was before Sauron's defeat.
That's my "extrapolated from the given information" reasoning, at least.
There's a new theory as to why the eagles weren't used here, which seems plausible.
Gandalf did intend to take the ring to the Eagles, but kept the plan to himself so that word couldn't get to Sauron. He tried to tell the Fellowship about the plan when he fell to the Balrog -- that's what he meant by "Fly, you fools".
My understanding was the Eagles have a will of their own. After all, Gandalf asked for permission to ride on their backs. Given this assumption, trusting them as companions to the Ring Bearer would not have been a good idea since they would be vulnerable to the ring's power of corruption. Also, it would be unlikely they would agree to a suicide run into Mordor.
I'm answering because I think there is an aspect of the use of magic in the LoTR that I commonly see ignored and is ignored in many of the answers.
One does not simply fly directly into the gaze of the Lidless Eye.
Enchantment vs. Magic
I am not a Tolkien expert, but my understanding of Tolkien's use of magic, I believe described in his "On Fairy Stories", distinguishes between a more mechanical kind of magic and a more spiritual "enchantment". Forgive/Correct me if I'm misusing his use of the words. It's been a long while since I've read it. There are many many examples of this enchantment, but some that spring to my mind are Faramir's description of the character of staves that he gives to Frodo and Sam, and of their experiences with the elven cloaks, roap, boats, etc. No concrete rules of physics are established. Instead, objects seem to vaguely bend the rules of physics in accordance with the atmosphere/nature of the object or their creator. And it's often not completely explained or even explicitly claimed. It is noteworthy that we're never conclusively told whether Sam's rope untied itself at his call or whether his knot was bad when they climb down the cliff at night. When the party is climbing Caradhras, they discuss whether the "fell voices" they hear are the wind or some creature. Tolkien likes to maintain uncertainty, and it's more about the mood & (spiritual?) atmosphere than the physics of what is occurring. Another example is the way the book describes the wills of Gandalf and the Balrog when they first confront one another on each side of a door, although that is a little more explicit. Also, when the 3 travelers Gimli, Aragorn, and Legolas are chasing the orcs who have captured Merry and Pippin, they talk of a hostile will that is set against them as they journey that is making their trek more wearying. Tolkien doesn't usually enumerate the way the different people and objects can manipulate the laws of physics like some other fantasy works of literature (in contrast to the use of the One Power in the Wheel of Time, for example). Instead, Tolkien creates "atmospheres" and "auras", for lack of a better word, around people and objects to give them a sort of personality, a nature, a character. It's part of what makes the conflict between good and evil so epic in the story, I think. Tolkien's use of wizardry and sorcery in LoTR is, in my opinion, more along the lines of "enchantment" (as referenced in "On Fairy Stories"), but I consistently see people treating it as a mechanical manipulation of physics. Gandalf is an interesting example, as we can name some specific mechanical feats he can accomplish with fire. But other things he does are more vague and more about who he is than any ability we could name. His power as compared in the story in the eyes of Pippin with Denethor, for example. (This is also why doing things like pitting Gandalf against Darth Vader in a fight don't work well, in my opinion. You have to decide which kind of magic/powers the fight will be composed of, and in my opinion, that determines who will win.) Aragorn is the same way, as is Faramir, Galadriel, and most of the characters in the book.
Sauron's Power is Firstly Enchantment, not Magic
One of the objections I saw raised to the eagle plan was that Sauron could conceivably throw fireballs at Frodo on an eagle, but I think this misses the point of Sauron's power. There is one part of the story where Gandalf says somewhat ominously that he has not yet been tested against Sauron. And Aragorn when he confronts Sauron with the Palantir barely has the strength to overcome him and wrest the stone away. It is mentioned that if the hobbits were captured, there is no doubt that in the end they would tell everything. And I don't think it would be in line with Tolkien to attribute this to merely physical torture. See Pippin's encounter with Sauron through the stone. I think you could attribute parts of this to some mechanical ability, but not all of it.
This is one of the beautiful things about Tolkien's writing that the movies could not or did not fully convey, I don't think.
The Eagle Plan Doesn't Solve the Real Problem of Sauron's Strength
I think the main reason why the eagle plan would not work is that few if any on Middle Earth have any hope of winning the contest of will that would occur in a direct flight straight into the Eye of Sauron, even without considering the draw of the Ring. The strongest good characters in the story are many times described as not certain of their ability to face Sauron's power directly. It's actually a question that comes up a lot, asked about Tom Bombadil, Gandalf, Aragorn, Galadriel, and Denethor, at least. And I don't think all these comparisons are meant to be military, even the talk about Tom Bombadil being overwhelmed as the guardian of the Ring or of Galadriel's contest of wills between her and Dol Guldur. It is not just, or even not primarily, Sauron's military strength that makes him formidable. In the books, his strength is more about force of will & malice & spiritual(?) presence.
Finally, when you add to the eagle flight scenario the Ring, which entices and draws the user according to Sauron's will, it becomes more impossible. Aside from confrontation with Sauron, both Galadriel and Gandalf have hinted that they feel they are not strong enough to be trusted with the Ring. I do not think they would count themselves strong enough to fly directly into the Eye with it unless perhaps they were to claim it for themselves.
Sidenote - Flying Unnoticed
To the argument that they might slip by Sauron's gaze unnoticed, I would first mention that Frodo has to battle against Sauron's gaze/will/power/etc without even being seen. Also I contest that they would likely be seen in the open sky, because this mysterious "spiritual" nature of Sauron's power applies to his sight especially, aside from any Palantir. (He is called the "Great Eye", after all). There are several examples in the books of characters like Gandalf (after the battle of Pelennor fields) or Aragorn (talking about the King's seat above Rauros), having or discussing experiences of seeing without a Palantir more from a high place than could probably be physically, mechanically seen. I'm not a medieval literature scholar but I would not be surprised if this idea was drawn from older romances and fairy tales. Hurin's imprisonment by Morgoth on a high place while he sees the lives of his children is an example of this as well. Considering Frodo's numerous experiences of being hundreds of miles away and feeling the Eye just moments away from seeing him, I think we can safely say that this is part of the nature/power/aura/enchantment of Sauron. How the palantir adds to this I am not sure, but I think it is more than physical sight. Also, the whole attack on the Black Gate was calculated to draw away his attention from his own lands, so his ability to see all that goes on in Morder is clearly a central concern in the story. For this reason, I think it would be especially risky to fly bare and unconcealed into the open sky into Mordor, even high up. There is a large chance they would be spotted, especially given the nature of the Ring. And once they were spotted, they (hobbit & eagle) would be confronted with the strength of all of Sauron's will and malice as alluded to above.
And of course on top of all this are the risks others have mentioned: Sauron's military might, the arrows of orcs and the strength of the Nazgul, who themselves have a terrible power of their own.
I just watched "The LEGO Batman Movie". Apparently, you can fly straight into the Eye's gaze if you are Barbara Gordon. But she's a special case.
@user296 hints at a possible reason but doesn't elaborate much.
I think that even though Gandalf can't see the future, he knows Gollum has a part to play:
even the very wise cannot see all ends. ... he is bound up with the fate of the Ring. My heart tells me that he has some part to play yet, for good or ill, before the end; and when that comes, the pity of Bilbo may rule the fate of many – yours not least.
(Fellowship of the Ring)
I think Gandalf knows more than he lets on. When Sam and Frodo fight about killing or abandoning Gollum we are again reminded that he has a part to play. Its kind of assumed that the part Gollum plays is leading them into Mordor. But I suspect that the real part he plays is in getting rid of the ring, and Gandalf knows this.
We know that it is near impossible to give up the ring. Only three times does the ring-bearer give up the ring:
- Bilbo, who doesn't expect it to be destroyed.
- Tom Bombadil, who is obviously "special".
- Sam, who isn't so close to Mount Doom to be totally overrun by its power.
So Gandalf suspects that the only way the ring can be destroyed is on accident. In other words there has to be some accident at Mount Doom to destroy the ring. He says somewhere that no one is powerful enough to destroy it. If the Eagles just drop Frodo off with the ring, there's a lot of evidence that he won't be able to destroy it.
- It is always seeking its master, not trying to be destroyed
- When he does get near to destroying it, Frodo hesitates
- Isildur was in the same position and didn't destroy it.
Who can say with any confidence that Gandalf didn't intend to use the Eagles, even if just for a section of the total journey?
After Gandalf dies, the members of the Fellowship are frustrated time and again that Gandalf did not reveal his master plan for getting the Ring to Mount Doom before his death. Strider in particular is repeatedly frustrated over the impossible decisions that keep arising on the journey and laments several times that his decisions were wrong in retrospect (from his limited perspective at the time, but not from the grand perspective of the story).
I don't think it's a stretch to theorize that Gandalf may have intended to make use of the Eagles in some way or for some segment of the journey; but, as others have mentioned, there's just NO WAY a giant bird is going to (A) sneak into Mordor and, further, to Mount Doom (keep in mind that it's a good ways into Mordor, just look at any decent map), and (B) get to Mount Doom without any risk of losing the Ring to Sauron right there in his own kingdom.
So, I can't believe the Eagle flying the Ring to Mordor would work at all, it's just not a viable option, but we don't know the entirety of Gandalf's original designs.
Here is a variant on the "Eagles would take the Ring for their own" theory. It has been argued that since powerful beings like Gandalf and Aragorn accompanied Frodo for months without trying to seize the Ring, an Eagle could do the same for the short time it would take to fly from the borders of Mordor to Mount Doom.
However the Ring has a will of its own. Tolkien makes it very clear that this is the case. For example, the Ring betrayed Isildur by slipping off his finger as he swam. Later, Gandalf observes that the Ring corrupted Gollum, but then abandoned him in order to escape from his cave under the Misty Mountains.
Now, let's take this concept and run with it. We can assume that the Ring's priorities are to survive and get back to Sauron. It can't understand spoken language, but it has some ability to sense the spirit world. Most of the time it is quite patient, for example spending several centuries with Gollum, but it can act more urgently if it so wishes.
During the journey of the Fellowship, the Ring was biding its time. It did not understand that it was in any particular danger. It may have been hoping to fall into the hands of Boromir, or some evil being such as an orc, the Balrog, or one of the Nazgul.
If someone takes it to the Cracks of Doom, the Ring is in a very different situation. It senses that it is in immediate danger of destruction, and will do whatever it can to survive. When Isildur first acquired it, Elrond advised him to throw it into the fire. Even though Isildur had only possessed it for a few minutes or hours, the Ring swayed his will and prevented him from destroying it. When Frodo approached the fire, he, too, was unable to bring himself to destroy the Ring. It was finally destroyed only because Gollum slipped and fell into the fire while holding it.
Now, suppose that an Eagle takes Frodo to Mount Doom. The Ring will exert all its power to save itself. It will call out to the Eagle, and there is a very good chance that the Eagle will answer, overpower Frodo, and seize the Ring for its own.
(Edit: As Frodo enters Mount Doom, it is mentioned that the Phial of Galadriel does not light his way, because all powers other than Sauron's are weakened. We can suppose that the Ring is correspondingly strengthened; although it is vulnerable there, it is also at its most powerful. This would make it more likely to be able to corrupt a nearby Eagle.)
I don't think this occurred to Tolkien. Otherwise, as the linked article points out, it would have been a good thing to mention at the Council of Elrond. But as a post hoc explanation for the plot hole, I think it makes sense within the rules of Tolkien's world.
They are not his to give.
Eagles are a race capable of their own actions and thoughts. The Eagles are not middle-earth taxis.
The eagles don't owe allegiance to anyone they helped Gandalf escape Saruman because he saved the life of their king, see the Hobbit. Nursing him back to health after an unfortunate incident with a hunters spear. Whether that help advanced to a suicide run into Mordor is another thing entirely...
If the Eagles could have taken the hobbits to Mt. Doom, they could have also delivered the dwarves to Smaug's lair, and though he was not a threat in the same way Sauron was, he weighed heavily on Gandalf's mind. So why did he only use the Eagles as a mode of rescue in dire situations, and as allies in a battle against dark forces?
Because Gandalf is a Maia, and is not supposed to directly interfere with the struggles of man and the creatures of Middle Earth.
In dire situations, where dark forces threatened to end such a quest, Gandalf may have called upon the Eagles, and in fact he did during his imprisonment atop the tower, and when the journey to end the threat of Smaug was threatened.
But Gandalf is the only one among the council who could have asked for the Eagles' help, and it was not his place to directly intervene. Even as he emerges as Gandalf the White, though he rode into battle and rescued the men of Helm's Deep, and was at the forefront of the final battle with Sauron, he was still acting only as a guide.
To have called upon the Eagles to carry the burden of the Ring would have been a gross abuse of his power as a Maia, and no matter how 'convenient' it would have been, he would not ever consider doing such a thing. And since no one else has the power to call upon the Eagles for aid, they wouldn't have considered it either.
Had he carried on with the Fellowship, instead of falling into battle with the Balrog, he may have called upon them once or twice for aid in desperation, but never as a final solution.
There has been a lot of discussion about using the eagles to fly directly to Mt Doom, and I won't go over it all again. I will point out a few things found in the LOTR books that are not often mentioned.
First: the Fellowship of the Ring has to hide on the way up the Misty Mountains (both in the book and in the movie). Why? Because there were thousands of Sauron-aligned evil intelligent birds moving everywhere and looking for enemies of Sauron. Clearly some were servants of Sauron and some were servants of Saruman, but in either case, the distinct sense I get from the book as written is that the air is largely full of enemies for the Fellowship. Why should we assume that it would be so easy to just fly into Mordor if there are possibly millions of evil-aligned flying creatures everywhere? The eagles would have had a long, continuous fight on their hands just to get there.
Later in the books, we see that after their "drowning" while trying to cross the border into Rivendell, the Black Riders have traded up their horses for "fell beasts" that were at least as big as the eagles and perfectly capable of patrolling the airspace over Mordor. It is extremely likely that these beasts were something that Sauron had in Mordor for some period of time, and people like Gandalf and Elrond were likely knowledgeable enough about some of the nasty things there that they would not have even attempted to just fly in. Again, flying in on a group of eagles when you are going to end up in air-to-air combat with ALL 9 riders on their fell beast steeds with no backup? That's even worse than going on foot!
Finally, we know from the Silmarillion and the Hobbit that "drakes" and dragons had often been aligned with Morgoth and his successor Sauron over the course of time. Elrond would have had good reason to think that Sauron might just have a dragon of some kind in his employ. Based on everything we know about Middle Earth dragons, the LAST place you would ever want to be would be staring one down face to face in the air with nowhere to find cover! If something like Smaug were to encounter the Fellowship of the Ring riding eagles, I wouldn't give them much of a chance, especially if the drake is backed up by 9 ring wraiths riding "fell beasts".
That only covers a few of the flying evil creatures that were hinted at in the books. There are repeated hints of worse and nastier things than were explicitly written about living in Mordor as Frodo makes his way across that land. It is very likely that some significant percent of the nasty creatures that had been drawn to Mordor by Sauron's call could fly!
I might also mention the fact that Saruman was capable of throwing a blizzard at the Fellowship as they tried to cross the mountains. Once more; being very easy to spot, but fast, puts them at risk of having that sort of magic thrown at them while airborne. A highly risky prospect.
Flying in on eagles would have been fast, but it also would have been pure suicide.
In the Hobbit, Gandalf did request that the Eagles carry them "far away and setting them down well on their journey across the plains below."
The response was:
The Lord of the Eagles would not take them anywhere near where men lived. “They would shoot at us with their great bows of yew,” he said, “for they would think we were after their sheep. And at other times they would be right. No! we are glad to cheat the goblins of their sport, and glad to repay our thanks to you, but we will not risk ourselves for dwarves in the southward plains.”
Similar reasons could be given for trying to fly across a continent while heavily laden with armored warriors (or even with just the hobbits, if they decided to risk sending them with only the eagles for protection). The eagles would need to take frequent rest-stops, and then they would have to take longer stops during which they would need to hunt.
During each of these stops they would need to land. Each of these stops would be potential ambush points (and as has been pointed out many times in these answers, they would not be traveling unseen).
Even without the danger of the Fell-beasts, which the Fellowship did not yet know of, fearing that the Nazgul mounted on new horses could likely intercept them at the many, many stops they would need to make between Rivendale and Mordor would be quite reasonable.
They have to do this in secret.
'And I will choose you companions to go with you, as far as they will or fortune allows. The number must be few, since your hope is in speed and secrecy'.
Additionally, Sauron's eye, The Witch King of Angmar and his Nazguls,The Mouth of Sauron as well as the orcs can easily spot them when they are in Mordor.
As a matter of fact, the video makes sense that this would happen if they brought the Eagles to Mordor.
I don't know much about vulcanology or what Tolkien knew about Vulcanology, but a volcano does not have a open vertical straight shaft going down to the magma all of the time. The vertical shaft is usually open only when lava is coming out, and then the flow of lava is upwards which would keep the Ring above the magma chamber. And when the eruption is over the lava in the shaft cools and solidifies and blocks the shaft.
And many volcanoes have non vertical twisting shafts.
And the Ring could only be destroyed in the Cracks of Doom inside the mountain because of the mystical magical need to destroy it where it was made.
So their goal was not to drop the ring in the crater at the top of Mount Doom and hope that would work, but to find the doors leading to the Crack of Doom, enter them, and throw the ring into the fires there, which for mystical reasons were the only place in the entire mountain where the Ring could be destroyed.
And if the eagles and their passengers were detected headed for Mount Doom, Sauron might use his control over the Mountain's fires to stop their plan. Sauron might turn off the fires in the Crack of Doom, so that tossing the ring in there would not melt it, and later retrieve the Ring before turning the fires back on. Or Sauron might make the mountain erupt furiously, spewing forth a miles-wide cloud of poison gas that kills the eagles and their passengers before they can land on the mountain.
So add that to the many other reasons, both correct and incorrect, that have been given as reasons why the Eagle Plan might have been a bad idea, reasons that Tolkien might have had someone mention in the Council if he had thought of the Eagle Plan.
The best answer is obvious. I'm going to tell that version of the story to show you why the Eagles didn't take the Ring to Mordor:
"Once upon a time, there was a magical Very Bad Ring. The Very Bad Ring could only be destroyed by the lava inside a certain volcano which was very far away. So the people gave the Very Bad Ring to some giant Eagles. The Eagles flew to the very far away volcano and dropped the Very Bad Ring into the lava. The Very Bad Ring was destroyed, and everyone was so happy that they threw a great big party and the Eagles were the guests of honor. Everyone sang and danced all night long. And they all lived happily ever after. The End."
Would you want to read a three volume, 1,200 page version of that story? I know I wouldn't.
All the in-universe answers are purely speculative in nature. This out-of-universe answer is the only one you need. The story would have been incredibly stupid and no one would want to read it - big birds flying to a volcano and dropping something into it just isn't an interesting story. There is no conflict, no tension, no drama. It would be the worst book ever written.
I think giant flying eagles flying into Mordor could have easily been spotted by Sauron and intercepted by the Nazgul. That would have given up the plan for the destruction of the ring in Mount Doom and handed him the ring. If the Eagles won the battle with the Nazgul in the air, then Sauron would have turned his attention to guarding Mount Doom and foiled the plan. In short, flying giant eagles in would not equate with "sneaking" in and either reveal the plan for the destruction of the ring or have given the ring to Sauron.
However, more fundamental than this: the eagles are essentially giant, wild animals, more aligned with the spirits of the forest such as Ents, Beren and Tom Bombadil. The battles of men and orcs, good and evil, are not part of their world high on the mountain tops in the wild. The "civilized" world of men and orcs is something they seek to avoid at all costs. They don't like creatures who destroy forests and create ugly buildings.
The eagles are definitely not anyone's pet or steed, they are wild, proud, intelligent animals, and have little to do with Gandalf except for the most dire of circumstances. They loathe unnatural things, orcs, Sauron, and the abominations of Morgoth. So flying into Mordor was something they were only prepared to do as a special gift to those who defeated the eventual threat to the natural world that the dominion of Sauron over all of Middle Earth would have represented, and only after the threat of Sauron and the Nazgul was removed.
For what I recall they didn't really have a plan to destroy the ring in Mount Doom. That's why they took a considerable amount of time to depart from Rivendell and why they were travelling slowly: they needed time to decide the best strategy.
The plan was along the line of: let's start going towards Mordor, which is probably the best place to destroy the ring, then we'll see what to do in due time.
protected by user56 Jan 18 '12 at 1:32
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