The Galactic Empire, in the form of Darth Vader's Death Squadron, has found the main base of the Rebel Alliance on the planet Hoth. All parts of Hoth that are seen in the movie are snow-covered polar climates.
After the Battle of Yavin, with the Death Star destroyed, Darth Vader became obsessed with finding Luke Skywalker and the hidden Rebel Headquarters Base. One of the later strategies he used was to send probe droids to a number of systems. One of them made its way to Hoth. Upon discovering a structure on the planet, it reported in. In fact, it was the best lead the Imperial Fleet had found at that point, Fleet Admiral Kendal Ozzel dismissed it, believing it might be smugglers or some other group. Vader overruled Ozzel's decision, certain the Rebels were hiding there.
The initial assault was met with some misgivings by various Imperial officers. They may have preferred a surprise attack with limited long-range orbital bombardment to destroy any gun emplacement, spacecraft and supplies — and then sweep in to capture the survivors. It was this plan that appeared to have the endorsement of Lord Vader, and seemed to be the original battle strategy. But Admiral Ozzel exited hyperspace too close to the star system, and Rebel early warning sensors detected the fleet. The theatre shield protecting Echo Base was activated, precluding any bombardment. Darth Vader executed Ozzel for his incompetence and promoted Firmus Piett, then-captain of the Executor, to Admiral. Vader then changed the battle plan, and ordered General Veers to begin the surface assault with his elite 501st Legion and Veers Blizzard Force Team. The 501st Legion participated in the ground assault as well as the naval blockade. Veers Blizzard Force Team consisted only of one mechanized division with minimum infantry involvement, but it was this division that pushed the primary assault to destroy the Rebels' primary shield generators. The Rebel Alliance never planned to win the battle. Its strategy was to commence a rearguard action: the battle only intended to buy as much time as possible for evacuation. As soon as the Imperial Fleet was detected, General Rieekan gave the order to raise the shield and begin the evacuation. Evacuation was via transports, escorted by a couple of X-wings with a heavy ion cannon providing covering fire.
This plan had been formulated in advance, with tow-cables outfitted onto the Rebels Snowspeeders due to anticipation that the main portion of the Imperial surface force would consist of 9 AT-ATs. The Blizzard Walkers employed heavy reflective armor that negated laser shots, missiles, heavy and light turret fire, so the Rebels used their tow cables to wrap up the legs of the AT-ATs and trip them. The first five Blizzard Walkers began the assault in formation, while the remaining walkers were spread out only to provide rear cover for the primary assault force by taking out aircraft, infantry and gun emplacements. Commander Luke Skywalker served as Rogue Leader for the defending squadron of snowspeeders, Rogue Squadron. His aircraft was shot down, but he survived the crash.
Battle of Hoth
The Imperial forces consisted of at nine AT-ATs and several AT-STs as well as ground troops. According to the Inside the Worlds of The Original Trilogy factbook, the force also included a number of AT-AR and AT-PT walkers. This Imperial Force was deployed by 3 Y-85 Titan Dropships; though the dropships did not appear in The Empire Strikes Back, they were mentioned in the ITW: OT factbook. The Rebels employed "snowspeeders" (modified T-47 Speeders), led by Luke Skywalker, and they had trench lines of anti-vehicle artillery and anti-personnel batteries (turrets) to fight a delaying action.
The Rebel troops discovered that their anti-infantry turrets and anti-vehicle batteries were unable to pierce the Imperial armour. Rogue Squadron, flying T-47 snowspeeders, also found their blasters ineffective, and used their rear tow cables to wrap around the AT-ATs' legs, tripping them up and destroying them in the process. Among the Rogues present at Hoth were Luke Skywalker, Wedge Antilles, Dack Ralter, Wes Janson, Derek "Hobbie" Klivan, Tycho Celchu, and Zev Senesca. It is later leared in Shadows of the Empire that smuggler Dash Rendar also flew with Rogue Squadron. Furthermore, in an act that centered out the Emperor's concern of him being a growing potential threat as a Jedi Knight, Luke single-handedly destroyed another by grappling up to the AT-AT's belly and throwing a concussion grenade in its power cells. Despite the escape of all senior personnel, the loss in material and men proved a disaster for the Rebel Alliance and the Empire had won its second major strategic victory after the destruction of the Death Star.
The elite snowtroopers, part of Lord Vader's elite 501st Legion ("Vader's Fist"), were attached to the Blizzard Force Team, assigned to Major General Maximillian Veers and the Imperial Navy. This stormtrooper battalion was well trained in combat on snow-covered worlds as well to be able to perform their missions as quickly as possible while employing anti-guerrilla tactics, which proved lethal to the Rebellion.
The Imperial assault was primarily aimed at destroying the Rebels' primary power generators. This would shut down the theatre shield protecting the base from orbital bombardment. General Maximilian Veers led the assault and crushed the Rebels' defenses, later, he destroyed the power generators. Once that had succeeded, Imperial forces could then deploy snowtroopers into Echo Base itself.
Approximately thirty GR-45 Medium Transports belonging to the Rebel Alliance, along with the Millennium Falcon, managed to take off but seventeen transports were destroyed by the Imperial naval squadron blockading the planet. The Falcon escaped by hiding in an asteroid field.
The battle was not without loss for the Empire: Imperial-class Star Destroyer Tyrant was disabled and heavily damaged by the planetary ion cannon, three AT-ATs were destroyed, along with some of their troops, by the Rebels and more were lost to the treacherous ice floes giving way. Despite forcing the Rebels to flee, it is not considered to be a major strategic victory because they were unable to destroy the skeleton force and threat of the rebels and failed at what Lord Vader considered to be a primary objective, capturing Luke Skywalker.
The novelization of The Empire Strikes Back has an alternate conclusion to the battle where the mortally wounded Hobbie Klivian rams his speeder into Veers's AT-AT, "killing" them both. In later Expanded Universe titles, both Veers and Hobbie appear post-Hoth alive and well.
The full Battle of Hoth has much more devastating losses for the Rebel Alliance than what was seen in the movie The Empire Strikes Back; particularly since the movie showed none of the evacuating transports getting destroyed.
In the video game Star Wars: The Empire Strikes Back, the first Star Wars video game ever released, the player controls a snowspeeder and tries to prevent the AT-AT walkers from destroying the power generator at the Echo Base.
In the video game Star Wars: The Empire Strikes Back (arcade game), the player can destroy AT-ATs with either harpoon cables or firing at their weak point in the Battle of Hoth. The stage ends when the power generator has been destroyed and the Rebel Alliance decides to evacuate.
The video game Star Wars Trilogy Arcade reenacts two parts of the battle. In the first, the player flies a fighter and takes out the AT-STs and AT-ATs. Afterwards, the player escapes from Echo Base.
The video game Star Wars Battlefront II includes a level titled "Our Finest Hour," which features the battle from the perspective of the Galactic Empire. In this level, the Empire destroys the Rebels' last transport, and finally the Rebels did not retreat. The Rebellion is destroyed once and for all. While this is the apparent ending of the game, it should be noted that during opening montage for the level the storyteller says that the vision for victory "might only have been mirage."
In "Tales of the Bounty Hunters", a compilation of stories of the galaxy's most dangerous Hunters in their search for Han Solo and Chewbacca, 4-Lom and Zuckuss damaged an escaping Rebel transport, bringing the total of captured ships to 17. After their meeting onboard the Executor with Darth Vader, the two used their ship, the Mist Hunter, to originally capture Rebel Controller Toryn Farr, her sister, and several other highly sought-after Rebel bounties, but because of Zuckuss' weak lungs were forced to transport the 100+ survivors to a Rebel sympathetic planet.
- Essential Guide to Vehicles and Vessels