Even though it is considered one of the most popular trilogies of all time, it doesn't mean there are no moments of stupidity.
You may put examples from both the books and Peter Jackson's film adaptations.
- During the prologue, at the Battle of Mount Doom, between the Last Elven-Human Alliance and the Forces of Darkness, Sauron shows up to personally turn the tide in his favor, with the power of the One Ring, and a huge mace. He manages to knock several soldiers around like golf balls, and manages to p'wn Isildur's father. When Isildur grabs his father's blade, he smashes it with his foot.
You'd Expect: Sauron would quickly finish Isildur with his huge killing mace, and kill him instantly. After all, just because you foot stomp and break a blade, doesn't mean it's useless, and can still be used as an improvised weapon.
Instead: He reaches his arm out to Isildur, intending to grab him and burn him, but is too slow about it, and Isildur cuts Sauron's fingers off, including the one with the Ring. It leads to Sauron's body blowing up, and he ends up (after the Ring continued to exist) existing as a flaming eyeball over Barad-Dûr.
- While Aragorn (aka Strider) is trying to lead the Hobbits (Frodo, Sam, Merry and Pippin) to safety from the Nazgûl (aka the Ringwraiths), the group stops at Weathertop to rest for the night. Aragorn goes to have a look around (patrol the farther area), and tells the Hobbits to wait.
You'd Expect: The Hobbits to wait patiently and not try to do anything foolish.
Instead: Sam, Merry, and Pippin make a fire while Frodo's asleep to cook their evening breakfast, tomatoes, sausage, and nice crispy bacon, which unfortunately gives away their position to the Nazgûl (aka the Ringwraiths), even when Frodo tries putting the fire out.
The Result: The Nazgûl attack the Hobbits, and Frodo gets impaled by the Witch King's blade, and is nearly killed as a result of it. This is an inverse of the book, where Aragorn ordered the Hobbits to build a fire, as the Nazgûl knew where they were and fire was their only ally.
- After Gandalf gets held captive at the top of Orthanc, Saruman's tower, Gandalf manages to have the moth go get one of the eagles to come and help him escape, which he does later. Saruman is at the top of the tower at the time.
You'd Expect: Saruman would summon a fireball (like how he does in the Extended Edition of Return of the King) and kill the eagle by burning it, along with Gandalf, so that he can't escape.
Instead: He just lets him go and makes no attempt to stop him from escaping with the fact that Saruman has allied with Sauron. Less of a problem in the book, since we don't see Saruman using fireballs (and some of Tolkien's notes give multiple versions of Gandalf's escape that agree on Saruman not being there at the time).
- Gandalf is adamant in his refusal to go to Moria, because the Dwarves Dug Too Deep and released the Balrog.
You'd Expect: Gandalf would explain this to the Fellowship. "We can't go there because there's a deadly fire demon" is not a complex explanation.
Instead: Gandalf only gives a vague answer that he would only go there if he had no choice, and when Saruman blocks the other paths, he punts the decision to Frodo rather than confess to his fears. Furthermore, even in this instance, Gandalf refuses to warn them until said demon is basically on top of them. Again, not a problem in the book because Gandalf didn't know there was a Balrog; the Fall of Moria had happened a thousand years in the past and all he and the Dwarves knew was that there was some vague but powerful danger.
For Added Stupidity: Up to this point, Gimli (who you'd think would be the first to know about his cousin's fate) has been constantly boasting about the hospitality of the Dwarves, having no idea that they're all dead, so Gandalf's refusal to go there makes even less sense because it looks like he's actively making the Fellowship take more dangerous routes rather than go through an area controlled by allies. Yet again, none of this nonsense occurs in the book, where Gimli and his father Gloin tell the Council of Elrond that they've lost contact with Balin's expedition to retake Moria and fear the worst, so the Fellowship knows that Moria is still rife with danger.
- The Fellowship arrives at the mines of Moria, but Gandalf has trouble figuring out how to open the door. Meanwhile, there's a pond right behind them.
You'd Expect: That everyone in the group would know good and well that doing anything foolish in an area as dangerous as this could cause trouble for the heroes, and ensure to stay quiet and try not to disturb anything or anyone who may be about. Doubly so considering they already dealt with the consequences of their foolish actions earlier when building the campfire, as mentioned above.
Instead: Merry and Pippin apparently haven't learned from their mistakes yet and throw rocks into the pond to pass the time, which awakens the Watcher in the Water and nearly gets Frodo killed. They only manage to get out of the situation by conveniently getting part of the mines to collapse on the Watcher, which subsequently traps the Fellowship and leaves them no choice but to go through the mines when they had just been reconsidering their decision minutes before.
You'd Then Expect: That Pippin would finally get the message and not go investigate a well they end up near while exploring the depths of Moria. Giving in to his curiosity has never turned out well for either him or anyone adventuring with him.
Instead: Pippin just has to go investigate the dang well. In the book he drops a stone into it, whereas in the film he touches a corpse's hand and the whole thing, plus a bucket with a chain, falls in. In both cases, any hopes of passing through Moria quietly are ruined, and it isn't long afterwards that the Company ends up having to fight their way through a bunch of orcs. Then things go from bad to worse because the orcs end up stirring up the Balrog, and they barely manage to make it out of Moria alive, minus Gandalf.
- When the Fellowship arrives at Amon Hen, Boromir leaves the camp to go get firewood.
You'd Expect: Boromir to bring his shield with him when going to gather firewood, in case there's the off chance that the enemy could launch a surprise attack and have protection against long range attacks.
Instead: He leaves it behind at camp. And unfortunately, the Uruk-hai launch a surprise attack on the Fellowship and he doesn't even go back for his shield quickly, and when he tries to go save Merry and Pippin, he is left defenseless against Lurtz's bow and arrow attacks, and is killed from the arrows as a result of it.
- The party of Uruk-hai that captured Merry and Pippin camp for the night near Fangorn Forest alongside a group of Orcs who joined up with them not long ago. Members of the party complain about the lack of decent food they've had recently, and a few Orcs consider eating Merry and Pippin. In response, the leader of the Uruks explicitly tells them that the Hobbits are to be taken to Saruman "alive and unspoilt".
You'd Expect: Everyone in the party would come to accept this fact.
Instead: One of the Orcs attacks the Hobbits, claiming that he just wants a nibble (from a part of them they won't necessarily need to survive or to march). He gets his head lopped off, and the party decide to eat him instead.
- Gandalf has freed Théoden from Saruman's evil influence. As the king comes to his senses, he realises that his advisor Grima Wormtongue has been working for Saruman the whole time, and therefore is indirectly responsible for the death of his son. In a rage Théoden ejects Grima from the castle and prepares to strike him down with his sword. Aragorn intervenes, arguing that "enough blood has been spilt on [Grima's] account." Théoden seems to agree with this.
You'd Expect: Seeing as Grima has been revealed to be in cahoots with Saruman, the evil wizard trying to destroy Rohan, that Théoden would immediately clap Grima in irons and take him to the dungeon. If they could get him to talk they could find out Saruman's plans. If not, at least they can let him rot for his treachery.
Instead: Théoden just lets him go. And not even as a royal pardon; he just stands there while Grima gets up and walks off. No-one in the whole of Rohan makes any attempt to stop the traitor from leaving.
The Result: Grima goes straight back to Saruman and reveals Théoden's plans and weaknesses, which Saruman exploits several times, nearly costing Rohan the battle of Helm's Deep. As in several cases earlier, this does not apply in the books, where Gríma, though allowed to leave (if any horse would bear him that is) and people are not to pick a fight with him, only makes it to Saruman when Saruman's tower Orthanc is already taken over by the Ents and the battle of Helm's Deep already won, so whatever weaknesses of Théoden's he revealed to Saruman that Saruman used in that battle were revealed before Gríma was found out as traitor.
- Gandalf goes to Minas Tirith with Pippin, where they meet Denethor, the Steward of Gondor. They tell him that the enemy is going to be on his doorstep.
You'd Expect: Denethor would listen to Gandalf, who has proven to be wise — if somewhat obtuse at times — and pretty much the one thing that can push the Nazgûl back. And even if Gandalf supports Aragorn as King of Gondor, it does not mean that he cannot maintain his position, advising the king on important matters.
Instead: He rebuffs Gandalf's quite sensible suggestions and rage about the fact that he'll never let Aragorn take the throne, saying that the throne of Gondor is his, and no other's. And in the film, when Pippin lights the beacon that will call Rohan to battle, at Gandalf's prompting, he gets angry with Gandalf. (Note: This is film only, in the books the beacons are already lit and the protective walls around the fields near the city are already repaired when Gandalf approaches, which makes the bit below make more sense.)
Then: He gets upset at Rohan for not getting to Minas Tirith fast enough, claiming his allies abandoned him.
- On the Frodo/Sam front of the story, during one of their resting breaks as they climb the Secret Stairs, Gollum throws the last of Lembas bread off the cliff to frame Sam for eating the last of it. Sam finds out the Lembas bread is gone! Frodo gets tricked by Gollum into believing that this is true, and tells Sam to leave and not follow.
You'd Expect: Sam to go "screw it", and still accompany Frodo. After all, like he said at the end of the first movie, "Don't you leave him, Samwise Gangee"! Alternatively, if Frodo flat-out refuses to travel with Sam any further, Sam would just try and follow him from a distance.
Instead: He obliges, despite knowing that he didn't eat the Lembas bread, breaks down, crying, and lets Frodo go on his own with the treacherous Gollum! In addition, he starts leaving and when he hit the bottom of the area, he sees the Lembas bread, and gets reminded of the fact that he didn't eat it! By the time he gets back up, Frodo has been poisoned by the giant spider, Shelob. Sam takes him for dead and abandons him to the orcs, though he takes the Ring first, and it is only the orcs' expositional banter that clues him in to Frodo's Not Quite Dead state. Frodo then gets taken to the Orc fortress of Cirith Ungol, necessitating a side trip by Sam to save him.
- The "Faramir being thought dead" fiasco. We expect Denethor to be unreasonable, but that doesn't excuse everyone else taking leave of their senses.
- Faramir reports that tens of thousands of orcs have taken Osgiliath, which he and just a few tens of soldiers have survived thanks to Gandalf's intervention.
You'd Expect: Denethor to listen to his son and realize that Osgiliath is lost for the moment, order the fortification of Minas Tirith and bring reinforcements and call for any allies that may be willing to come.
Instead: He rebuffs Faramir's claims, saying that he and his men ran away because of cowardice, and orders him to lead a small army to retake Osgiliath, which leads to disastrous results.
- Faramir's attempt to retake Osgiliath ends in failure with the entire unit wiped out, except for Faramir and his horse. Faramir is knocked unconscious from a poisoned arrow, and Denethor assumes he's dead. Pippin, however, notices he's still kicking, saying, "He needs medicine, my lord."
You'd Expect: Denethor, as grief-stricken as he is right now, to listen to what Pippin's saying, which would give him a sign of relief.
Instead: Denethor ignores that, yelling "My line has ended!" When he sees Sauron's army at his doorstep, thinking Rohan will not aid him, he yells "ABANDON YOUR POSTS! FLEE! FLEE FOR YOUR LIVES!" Gandalf at least corrects for this last bit of stupidity by knocking him out and rallying the defenders, yelling, "Prepare for battle!", but this leads into something even stupider.
- Just to take stock, Denethor is now unconscious, and Pippin is presumably still by Faramir.
You'd Then Expect: Pippin would get someone, anyone, to drag Faramir to the House of Healings, or do the task himself, saving his life. Or at the very least, bring the poor guy some medicine.
Instead: Against all logic, everyone completely forgets about Faramir, and leaves him and Denethor up there in the courtyard while they go to defend the city, including Pippin, who knows for a fact the guy is alive. This becomes a waste of time for Pippin, who is told to go back to the Citadel as requested by Gandalf. Unfortunately, by the time Pippin gets back, Denethor woke up, and is still under the delusion that his son is dead, and decides a Viking Funeral is in order.
- When Denethor carries Faramir's unconscious body to the Tomb of the Stewards, to kill himself along with Faramir, he tells his members of the Citadel Guard to "bring wood and oil" for the funeral pyre.
You'd Then Expect: Given they've already seen their steward try to abandon defense of the city and get laid out by a wizard for his stupidity, they'd respond with a "You're Insane!" and lock him up for being demonstrably crazy. Pippin said Faramir was alive, and these guys surely must have heard him. At the very least, they are assisting in the willing suicide of their leader, which no sane person would do in time of war (unless you have 100% lost).
Instead: They continue blindly following Denethor's orders without question like it's a brilliant idea (What?!?), despite the fact that he has clearly lost his mind, and don't even seem to care that they might be burning Faramir alive.
Worse Still: When Pippin comes in, yelling "HE'S NOT DEAD!" and trying to save Faramir by taking the pyre apart.
You'd THEN Expect: At least one of the guards or anybody that isn't Denethor to stop and ask Denethor something like, "Sir/My Lord, what if he's right?" Even though Denethor's an a-hole, asking is at least better than nothing.
Instead (!!!): The guards straight up ignore Pippin like brainless idiots as Denethor drags him out.
Even Worse: In the book, one guard does come to his senses and tries to save Faramir, but unfortunately, he ends up facing resistance from the rest who continue to follow the crazy guy's orders.
- Once Pippin gets thrown out of the Tomb of the Stewards, Denethor tells him to go away and die in what way seems best for him, and closes the doors. This ends up leading to idiocy on both sides. First off, nothing is stopping Pippin from walking back in.
You'd THEN Expect: Pippin to open the doors, walk back in, maybe try to talk some sense into the guards or anyone who isn't Denethor.
Instead: Apparently writing the idea off as a lost cause, he immediately gives up, and instead runs through the city currently being overrun by orcs to get Gandalf for help, taking all night to accomplish this, risking not only his life and thus Faramir's by extension, but possibly wasting enough time for Denethor to burn himself and Faramir alive.
- As for Denethor...
You'd Expect: Denethor would lock the doors, ordered them barred, maybe send one or two of his Yes-Man guards out to keep watch.
Instead: None of this happens. Pippin could have just walked back in, and Gandalf eventually comes charging in on horseback.
- Once Gandalf finally shows up to "stop this madness", Denethor grabs a torch from one of his guards and lights the pyre (in the extended edition, before doing so, he says (true to his book counterpart's opinion), "You may triumph in the field of battle for a day. But against the power that is risen in the East, there is no victory.").
You'd Expect: If Denethor is really this set on killing himself, he would go all in and have his guards hold the line against Gandalf, who will doubtless interfere.
Instead: He does nothing of that sort, and Gandalf grabs a spear from the nearest guard (who for some reason, doesn't stop him) and knocks Denethor off the pyre, allowing Pippin to push Faramir's body off the pyre and save him from being burned to death. When Denethor threatens to do something terrible to Pippin while yelling, "You will not take my son from me!", he gets knocked into the pyre by Gandalf's horse. As he finally realizes his son is in fact alive, he gets set on fire, and runs all the way out of the room and jumps to his demise.
- Faramir reports that tens of thousands of orcs have taken Osgiliath, which he and just a few tens of soldiers have survived thanks to Gandalf's intervention.