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As demonstrated in the beginning of Phantom Menace, lightsabers can easily slice through or melt metal. Why didn't Luke just slice the feet or legs off the AT AT Walkers in The Empire Strikes Back?

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    your reference to phantom menace also leaves out the part about the blast shield, and qui gon had to slowly melt the door down, and couldn't just cut right through it, now i assume atat's are build with similar high grade metal, they are quite thick, as well as currently moving. it was much simpler and fast to just blow it up. – Himarm Sep 30 '14 at 13:10
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    Following @Himarm here, and bringing it into the real world a bit: it looked cooler to just blow it up. Back in-universe: explosions are frightening and kill lots of people, which is what terrorists like the Alliance to Restore the Republic were all about. They really liked to blow things up and kill lots of people. If Luke had simply amputated the AT-AT's "foot", the machine might have stumbled and collapsed, but likely would not have exploded (thus all the troops and equipment carried inside would survive and could present a continued threat). – Adrian Sep 30 '14 at 19:46
  • Things are so much simpler for heroes in anime, who typically have sword beams to augment their attacks. – Blazemonger Oct 1 '14 at 14:20
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Why he didn't

The most plausible answer is that he just didn't consider it. By the time of the attack on Hoth Luke had received essentially no formal lightsaber training, and had only owned the weapon for about 3 years. Compare that to Qui-Gon, who had decades of experience with lightsabers, and Obi-Wan, who had received extensive formal training. It's exceptionally plausible that Luke just didn't know what a lightsaber was capable of yet.

But what if he had?

I don't think it would have been as easy as you think. What you need to remember is that different grades of metal are used for different purposes.

The scene at the start of Phantom Menace shows Obi-Wan and Qui-Gon facing off against B1 battle droids, standard infantry units designed for mass-deployment. They're lightly armoured for mobility and cost-efficiency, and about as thin as a humanoid skeleton. A lightsaber cuts through them like butter, because they're not meant to withstand any serious resistance.

Compare to when Qui-Gon tries to get through the door to the command center. He can penetrate the door easily enough, but cutting through it requires significant effort. Once the blast doors are closed, it becomes even more difficult. The following gif shows the results of his efforts: the first bit of damage you can see on the inside of the blast door took Qui-Gon minutes to achieve,and the gif itself shows him putting his entire strength (And probably some of the Force) into one thrust, which succeeds in knocking off a panel about the size of a sheet of paper.

Qui-Gon versus the blast door

And that's the blast door on a space station. The worst firepower they would expect would be from a heavy-weapons turret.

The AT-AT was possibly the most heavily-armoured ground unit in the Imperial fleet. It was designed for large-scale tactical assault, presumably against heavily-fortified positions and the strongest turret emplacements you could put on land. The Star Wars Encyclopedia states that they were armoured with some of the heaviest Durasteel available, impenetrable to all but the most powerful artillery. Part of the trouble the rebels have with them on Hoth is that none of their guns, even the turret emplacements, so much as scratch their armour.

Leaving aside the issue of armour for a moment, look at the size of it:

sweet mother of mercy that thing is big

This isn't an official image, but it illustrates the scale of the thing: that tiny black speck between its legs is Luke, hanging on by his grappling hook. I doubt he's as big around as the axle in the AT-AT's ankle joint. Even leaving aside the issue of the armour, trying to cut that thing down with a lightsaber would be like trying to chop down a giant redwood with a herring.

Although I have little doubt that a lightsaber could cut through an AT-AT's armour, it would take such a long time that it wouldn't be worthwhile.

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    +1 for the beautiful metaphor "trying to chop down a giant redwood with a herring" – user20155 Sep 30 '14 at 6:01
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    Fact is that lightsabre effectiveness is wildly inconsistent even within the same scene - see Luke's two handed swing bouncing off Vader's shoulder and moments later Vader effortlessly cutting through a huge bunch of pipes by accident. But you've come up with a good example showing the limits of a lightsabre when used for industrial scale metalwork so +1 – Grimm The Opiner Sep 30 '14 at 9:30
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    More to the point, if he chopped off a foot the thing would topple right then and there. Quite possibly on top of him. – Shadur Sep 30 '14 at 10:39
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    @GrimmTheOpiner I'm pretty sure that unlike the pipes, Vader would use the Force to protect himself during battle. – Cees Timmerman Sep 30 '14 at 10:51
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    @GrimmTheOpiner There are various materials in the Star Wars universe which are far more resistant to lightsabers than other metals. It isn't unlikely that Vader's armor was enriched with these materials to protect him in case he needed to face any of the remaining Jedi in lightsaber combat. When he got his armor Obi Wan just beat him once and he was still alive, so this would have been a reasonable precaution. – Philipp Sep 30 '14 at 10:54
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I prefer to think that "cutting through matter of significant thickness and density" (as opposed to piping, handrails, or wrists) is something that didn't occur to the screen writers during the creation of the original trilogy.

Take the Bespin fight scene, toward the end when Vader and Luke step out into the big shaft. At that point, Vader misses Luke twice, hitting the wall to his right instead -- about the only time I can remember from the original trilogy where a lightsaber strikes something really solid. Vader's lightsaber glances off, there are some sparks, but the wall remains undamaged. There is no slash of glowing, molten metal, like when a lightsaber hits a wall in the prequel trilogy.

I.e., my explanation is that the effect of lightsabers on solid matter was quite different in the mind of Lucas et al. back when the original trilogy was being made.

Actually, the "old" way is much more consistent with the explanations on how a tiny device like a lightsaber could actually create such a powerful blade for a prolonged time, as given by the West End Games "Star Wars" RPG back then: The power of the blade is only actually used up when it strikes something. I.e., a feat like Qui-Gon cutting through blast doors would leave the lightsaber's power unit depleted in no time... something which I actually expected to happen when I watched Phantom Menace the first time...


Reviewing the AT-AT footage, there's another point... the pylons are massive. The "feet" are circular disks almost as tall as Luke himself, with virtually no hand- or foothold, and moving at significant speeds, let alone jerking quite violently on each step. Trying to scale one of those to get at the thinner "leg" while the AT-AT is moving is... risky, to say the least. Aiming his grappling hook at the underbelly -- which is moving at a constant pace and doesn't threaten to crush him on a failed attempt -- seems like the much smarter thing to do.

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    This squares with my view that Star Wars is a medieval tale in space costumes. Lightsabres are swords; you wouldn't bother trying to cut through something with them, they're for poking fleshy humans. And they go whijj. After the first 3 films that gets diluted somewhat because they treated it more like SciFi and less like Robin Hood. – Phil H Sep 30 '14 at 12:52
  • @PhilH: The technical term here is "space opera". However, I don't feel that the prequels were any more or less "SciFi" than the original triology. Starships still moved in violation to basic physics, and "the science" was never really part of the plot. – DevSolar Sep 30 '14 at 13:49
  • Editors: Spoilsports. ;-) – DevSolar Oct 1 '14 at 4:31
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The sheer size of the AT-AT would likely make it difficult to sever the AT-AT's feet. Here's a screenshot of Luke as he is about to destroy the AT-AT:

enter image description here

As you can see, the feet and legs are very large compared to Luke's body. The AT-AT appears to have a bit of a weak point at the four connectors between the feet and legs, but even these are very large compared to Luke (they appear to be about as wide as he is) and he would probably need to cut through two of them to ensure the foot was severed.

Moreover, the AT-AT was moving so it would have been difficult for Luke to maintain his balance and apply force while cutting through the armor. Although Qui-Gon was able to cut through a blast door in The Phantom Menace he was able to do so on stable ground, and it took him considerable time to do so.

Luke destroyed the AT-AT by cutting into its underside and throwing an explosive inside it. The Wookieepedia article on the AT-AT notes a weakness on the underside:

The AT-AT also lacked armor covering on its underbelly, leaving the spot vulnerable to mounted guns or portable missile launchers. To remedy this weakness, AT-STs were usually stationed around the flank of the walker to ensure nothing was given a clear shot at the AT-AT's weak underside.

The weakness was significant enough to affect Imperial battle formation. It is entirely possible that Luke was briefed on this weakness before the battle, and even if not it would be a reasonable assumption that the underside was not as well armored. On the other hand, one would expect the AT-AT's feet to be well armored since they are critical to the AT-AT's ability to move and they are more likely to come under attack (e.g. by infantry armed with explosives).

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    Wow, so the weight of the AT-AT is supported by the four flimsy looking connectors? Doesn't look stable. – RobertF Oct 1 '14 at 5:37
  • @RobertF 16, 4 per leg :) And flimsy? Durasteel girders the width of a full grown human? – jwenting Oct 1 '14 at 12:00
  • @RobertF They do seem pretty unstable in the movie! I would hate to ride in one. – TylerH Oct 1 '14 at 14:18

protected by Community Oct 1 '14 at 20:06

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