(This question is related to How did the AT-ATs get to the surface of Hoth?, and was originally posted as an answer there, but it's not the same)

A group of AT-ATs approach Echo Base

In The Empire Strikes Back, the Empire attacks Rebel Echo Base located in Hoth. The Rebels are alerted before the attack, and raise some sort of shield to prevent orbital bombardment of their base. The Empire is then forced to deploy land forces to first disable the shield generator, before destroying the base. Presumably, the Imperial forces are deployed using dropships.

My question is about how the Rebel shield generator works, and how the Imperials manage to bypass it.

I think the shield generator is something of a plot hole. At first I incorrectly thought it was a planetary shield (i.e. a shield around all of Hoth) preventing orbital bombardment, and also preventing any dropships (with their AT-AT payload) from landing, but I think Wookieepedia got it wrong: the script states it is an energy field around just an area of Hoth, presumably Echo Base:

VEERS: My lord, the fleet has moved out of light-speed. Com-Scan has detected an energy field protecting an area around the sixth planet of the Hoth system. The field is strong enough to deflect any bombardment.

So my initial objection ("how did the Imperial dropships bypass the shield?") has been answered: they didn't. They landed outside the energy field to deliver the AT-ATs. But now I have another question: does an AT-AT have to walk inside the field to fire at the generator, or can it fire into the field from outside?

Maybe the field simply cannot stop matter, only energy weapons (therefore preventing orbital bombardment), in which case the AT-ATs would be able to just walk inside. However, the script also states:

LEIA: All troop carriers will assemble at the north entrance. The heavy transport ships will leave as soon as they're loaded. Only two fighter escorts per ship. The energy shield can only be opened for a short time, so you'll have to stay very close to your transports.

So it's clear that the energy field is also capable of stopping matter, in this case troop transports and fighters. It follows that it should also prevent AT-ATs from walking through it. So the only way I can see the walkers disabling the generator is by firing into the energy field!

This would mean the field is strong enough to stop matter such as ships and fighters, and energy weapons used for orbital bombardment (and also the Ion Cannon the Rebels use as an anti-orbit battery: Leia also states they must lower the shield to use it), but not able to stop whatever energy weapons the AT-ATs use!

So how on Earth did Imperial Walkers manage to disable the shield generator?

  • 6
    I don't know about the Star Wars shields but in various universes shields aren't able to stop slow objects from going through them--the blocking is related to the speed of the item being blocked. Thus something that stops a blaster bolt cold merely offers some resistance to a walker. Commented Jan 21, 2012 at 18:34
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    @LorenPechtel: you mean like the shields in Dune, right? It makes sense.
    – Andres F.
    Commented Jan 21, 2012 at 20:14
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    It is conceivable that the shield poses a threat to the ships because of their energy output being disrupted by the field. So while it wouldn't stop the matter, it would probably shut down the ship's computer systems, leaving a useless, broken hunk of metal passing through the other side.
    – corsiKa
    Commented Jan 22, 2012 at 0:56
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    @AndresF. - "How on Hoth did they manage to disable the shield generators?", surely?
    – Valorum
    Commented Dec 22, 2014 at 20:03
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    @AndresF. I've just re-watched the scene and Veers says "an area of the sixth planet of the Hoth system", which kinda makes my point moot :)
    – Rawling
    Commented Nov 12, 2016 at 14:30

11 Answers 11


I'll posit an alternative hypothesis to zephyr's.

I recall some mention that the shield did actually stretch all the way to the ground, but it was of a type that didn't impede the AT-ATs because they're relatively slow. Such shields do exist within the SW universe:

The Gungan shields used during the Battle of Naboo blocked lasers, but droids could pass through because of their relatively slow movement in comparison to the laser bolts. Some shields only held back anything with a high-energy output, allowing sentients to pass through unharmed.

The relevant Wookieepedia entry doesn't specify which type of shield it is, unless you take "umbrella" to mean not reaching the ground. Possible, but I don't think it's a certainty.

Two reasons this could be the case:

The alliance was fairly limited on tech and scientists. The base took two years to construct, and was invaded about a year thereafter. It could well be that it's much easier (in time and resources) to create an energy shield, and the scientists they brought to create the shield set one of those up first (possibly planning to upgrade it later).

And I'm pretty certain there is a mention of another modern shield of this type somewhere in the EU (but I don't remember where and that's a lot of material to scour), indicating they were still in use well after Hoth.

  • In the game Star Wars: Rebellion, you had to either sabotage planetary shields or overload them with a larger bombardment in order to land troops.
    – surfasb
    Commented Jan 21, 2012 at 19:30
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    The personal shields used during hand-to-hand combat in Dune had the same vulnerability: they stopped fast attacks but a slow knife could slip through. AT-ATs are nothing if not slow.
    – Adam Wuerl
    Commented Jan 21, 2012 at 20:36
  • I'm going to accept this answer, even though zephyr's also makes sense. This explanation, while speculative, doesn't rely on anything but tech shown in the movies (the Battle of Naboo). The shields don't look the same, but the tech could be similar. The alternative explanation requires we believe "umbrella-shaped" means the shield doesn't touch the ground.
    – Andres F.
    Commented Jan 21, 2012 at 20:54
  • There's an episode of the clone wars where Asoka is teaching some locals how to fight Droidekas. She shows them how to throw a thermal detonator slow enough that it makes it just through the shield, and then blows up inside. The point is that it has to be moving very slowly. Commented Mar 8, 2015 at 17:55
  • We also see specialized shields in basically every ship hangar. Ships can pass, but oxygen, people etc. stay inside the ship or station.
    – Kakturus
    Commented Feb 10, 2020 at 14:00

The most obvious answer is that the energy shield does not extend all the way to the ground. This would make sense, since the terrain is mountainous and uneven. Instead it could form an umbrella above the base that prevents shots and ships from passing through, but which the AT-ATs could simply walk under the edge of.

  • 2
    Supported by wookiepedia: starwars.wikia.com/wiki/Theater_shield
    – so12311
    Commented Jan 21, 2012 at 16:16
  • Damn. Too fast for me. +1 Commented Jan 21, 2012 at 16:57
  • Excellent answer! Though it does seem like an afterthought from the Extended Universe ;)
    – Andres F.
    Commented Jan 21, 2012 at 17:26
  • Yeah, I didn't like how apparently this is a brand new piece of technology recently developed by the rebels - it seems like someone would have thought to put a shield over a military base before.
    – so12311
    Commented Jan 21, 2012 at 18:32
  • Yeah, they probably can't make the shield perfectly conform to the terrain. If the shield can keep out objects you certainly don't want it touching the ground. Commented Jan 21, 2012 at 18:32

Perhaps I'm remembering incorrectly, but I believe the reason they dropped the shield is so that they could then shoot the ion cannon that they had on the surface and disable the Star Destroyer that was in the way. This way the transport and small X-wing complements could just fly past and enter hyperspace without having to deal with a drawn out space battle. I imagined Leia telling the pilots to stay close to the transport was meant in case they missed or something and therefore they needed to make sure they're not flying too far away from the transport because it would need immediate protection.

Leia's reminder is still a little weird in this case (if you're on escort duty, I'm not sure why you would be flying away) but I think it still fits.

In this way, the shield generator was meant to stop energy weapons, which would include the ion cannon. Hence they need to drop the shield in order to fire the cannon. Matter could bypass it.

  • Your answer also makes sense. But then, couldn't the Imperials simply drop kinetic/explosive weapons on top of the Rebel scum? You know, like... good old-fashioned bombs :P If not from orbit, then at least from bombers.
    – Andres F.
    Commented Jan 22, 2012 at 15:38
  • A good point. Perhaps a mix of this and Kevin's answer would make the most sense.
    – The Jug
    Commented Jan 23, 2012 at 0:08
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    @AndresF - As I recall, Darth Vader didn't want to simply pound the Rebel base into oblivion from orbit - he wanted to capture the base (presumably to interrogate prisoners & snoop thru their computers to find clues to the location of the Rebel Fleet). More importantly, he wanted Luke Skywalker alive.
    – RobertF
    Commented Jun 19, 2014 at 18:18

Like in Dune, the slow knife walker penetrates the shield. The shield was designed to repel energy and high velocity particles. Wookieepedia states the AT-TE (a previous design) could walk right through it...

An AT-TE was impervious to ion damage due to built-in electromagnetic shielding. Its average speed was 60 kph (37.2 mph). This plodding pace allowed it to penetrate energy shields, a feat that was impossible for repulsorlift craft.

In addition, the Hoth shield was an umbrella shield only designed to defend against orbital bombardment. Presumably it came low enough to the ground to prevent low flying aircraft from entering (TIE Fighters aren't good enough in atmosphere to risk it), but it was generally oriented up. AT-ATs and ground troops could walk under it.

  • This may also be a good explanation why an AT-AT is preferred over a repulsor lift tank in this recent question: scifi.stackexchange.com/questions/76087/…
    – RobertF
    Commented Dec 19, 2014 at 19:31
  • It seems odd that the repulsorlift craft couldn't just slow down when they reach the shield. Even if they don't have a throttle for some reason, the driver could just put it in neutral and let the infantry push it through the shield.
    – Ray
    Commented Jan 11, 2018 at 19:12
  • @Ray They'd then be easy, lightly armored targets on wide open terrain where the Rebels would set up a kill zone. AT-ATs are the infantry tanks of Star Wars: slow and heavily armored to break static defenses. Similar to how a mine field is less about killing the enemy, more about slowing the enemy down and channeling them into kill zones. (Out-of-universe answer: that's not a cool Star Wars battle).
    – Schwern
    Commented Jan 11, 2018 at 19:38

This was addressed by Pablo Hidalgo in Star Wars Insider #90. In short, the shield extends upwards and outwards, but leaves gaps at the sides.

Q. I am confused about something I noticed in The Empire Strikes Back. On Hoth, the Rebels need to open the shield generator surrounding the planet to let out the first transport, along with the two X-wings. If the Shield generator needed to be opened to let a transport out, how does the Empire manage to get a Star Destroyer in to deploy the AT-AT?

PH: The energy shield that covered Echo Base on Hoth only offered a limited protection of a few kilometers from the source. Think of it as a ceiling above the Rebel base. It definitely stops Rebel ships from taking off and guards against bombardment, but does nothing to stop Imperial ships from arriving in the system, high overhead. That's why, as Vader ordered, General Veers had to land his troops beyond the range of the energy shield, and then march overland under the shield “umbrella” to destroy the power generators.

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  • A late but very illustrative and definite answer! Thanks. I see SW Insider is "official", but how canon would this answer be? (It looks intuitively right to me). If this is officially true, I think I'll change the accepted answer to this one.
    – Andres F.
    Commented Jan 5, 2023 at 14:39
  • @AndresF - Like everything written pre-2014, it's Legends unless confirmed in canon. That being said, I can't imagine they'll contradict this.
    – Valorum
    Commented Jan 5, 2023 at 18:54

The Star Wars Battlefront II videogame best explains this. The last mission of the campaign was Hoth. The shield was protecting the transports, which were settled in a small basin behind Echo Base. The shield generator was in front of Echo Base's hangar. The Rebel offensive line was between the shield generator and Echo Base's hangar, facing downrange.

The Empire had two goals during this battle:

  • Have Blizzard Team (the first wave, featuring AT-ATs, etc) destroy the shield generator.
  • Advance on Echo Base, clear out any rebel forces, and capture the base.
  • Darth Vader & co will then proceed through Echo Base to the Rebel evacuation point (the basin where the transports are) to place a targeting beacon for the Star Destroyer to home in on to bombard the immediate surrounding location.

In short, the shield generator was nowhere near the shield itself (I know, right?). If it wasn't for it being so theatrical, Gen. Veers and Blizzard Team could have just landed right at the rebels' door step (just outside EB hangar), but the calm before the storm builds tension and is much more dramatic in a war movie.


My theory is that you can't shoot or fly through a shield, but you can walk and probably roll through them as long as you remain in contact with the ground. Theater shields have been used twice in the movies (Battle of Hoth and Battle of Naboo). At Hoth it is established that the shield can withstand bombardment so they land AT-ATs which walk through the shield then destroy the power generators so the rest of the attack can land. During this entire sequence the much better equipped Imperials have no air support just heavily armored walkers. At Naboo, it is established that the shield can withstand bombardment from the tanks, the Trade Federation sends in its droids which destroy the generator so the hovering tanks can attack. If something solid can pass through why didn't the Gungans fire their catapults at anything outside of the shield. If something slow moving can pass through the shield, why didn't the tanks just slowly fly through them instead of waiting for the shield to get destroyed. This also explains a couple of weird things like why the Vulture droids (which are starfighters) are designed with the ability to walk and why the Empire uses walkers instead of hovering transports.


I don't know what level of Canon the old Rogue Squadron games were, but I remember playing the Hoth level. If I'm not mistaken, the shield generators did not shield themselves. At the time (as a ~10 year old) it seemed like quite a major design flaw....

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    do you mean they generator was outside the shield? Sounds like a huge flaw! Wouldn't the Imperials be able to attack the generator from orbit, then?
    – Andres F.
    Commented Jan 21, 2012 at 20:13
  • Only if they were able to see it from space, if my memory serves the shield generator was quite small. Commented Jan 21, 2012 at 20:44
  • @AndresF. I have no idea....!
    – AncientSwordRage
    Commented Jan 21, 2012 at 21:26
  • The same design flaw was present in RotJ - the Imperial shield generator on Endor was unprotected. At least I'm assuming it was if Han, Luke, & Leia could approach on foot. So wouldn't it have been simpler to forgo the secret commando mission to blow up the shield generator, and just lob a bunch of missiles at the generator from orbit as soon as the Rebel fleet exits hyperspace?
    – RobertF
    Commented Jun 19, 2014 at 18:01
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    As I understand it, pre-Disney, the LucasArts games (including the Rogue Squadron series) were full canon. You can get the PC version of Rogue Squadron on Steam today, and it will work with an xbox controller. :)
    – blaughw
    Commented May 27, 2016 at 20:57

The game, Star Wars Battlefront, specifies that the Empire deployed a special division of Stormtroopers to take the shields out. The walkers carried these troops safely into the barrier and the troopers secured the area around the shields before the walkers destroyed them.

The troopers were most likely acting as insurance in the off chance a rebel guarding the generator was carrying a heavy ordinance weapon.


The shield is an umbrella shield that blocks both energy and matter, but it's atmospheric. It is purely a defense against aerial bombardment, and the generator isn't strong enough to protect an entire planet. It is not a ground defense. Unlike, say, the Millennium Falcon which can focus its shields on different parts of the ship, the front or rear, the Hoth shield can only be focused in the "up" position and is either on or off. As said above, the At-Ats can be dropped outside the perimeter of the shield and walk in underneath. It's a flaw in Hoth's defences, (obviously was necessitated by the story) BUT, to Lucas's credit, he's consistent. It's a defensive flaw the Rebels themselves are obviously aware of, with their networks of defensive trenches and laser towers.

Leia's admonition to "stay close to the transports" makes sense precisely because the shield stops both energy and matter. If the x-wings get too far ahead of the transport they will be pulverized by hitting the shield before it's lowered. If they lag too far behind they risk crashing into it after it's been raised again.


The Gungan's had portable shield generators that stopped incoming fire from the droids and tanks. But the droids and tanks could simply walk through the field.

Other than Leia's comment about briefly dropping the shield to allow the shuttles and X-wings to leave, it would be easy to believe the Hoth shield worked the same way.

The Gungan shields were projected upwards and did appear to be thicker up higher, so perhaps the shield it more impermeable the closer to the point where it is being initially projected.

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