The Battle of the Hornburg from Peter Jackson's The Lord of the Rings: The Two Towers.
Fans and readers refer to the battle as "Helm's Deep", but that refers to the ravine in which the fortress is located. The actual fortress consists of the Deeping Wall and a fortress-like tower, the Hornburg. A cave in the rear of the ravine was known as the Glittering Caves, or as Aglarond. Tolkien asked that the battle be "the defense of the Hornburg" or "the battle of the Hornburg".
In the novel, Théoden rides to the Fords of Isen to find what is left of his in-the-field command. Discovering few men have survived, he follows Gandalf's advice and takes his troops to the Hornburg fortress. Gandalf remains behind with Erkenbrand (not Éomer) to gather the militia. The battle is pretty straight-forward: The Uruk-hai and men of Dunland attack, and are temporarily held at Helm's Dike (a raised earthwork at the mouth of the ravine). The Uruks and Dunlendings attack again, and the dike is overwhelmed. The Uruks and Dunlendings attack the Hornburg but are rather easily repulsed. They attempt to breach the Hornburg, and almost do so (begging the question as to why a drawbridge doesn't help defend the tower). But they are repulsed when Aragorn and Éomer ride out on horses through the gate and break the Uruk forces. The door is reinforced. Around 2 AM, the Uruk-hai use gunpowder to blast their way through the Deeping Wall. A fierce battle erupts, but the Rohirrim retreat into the Glittering Caves -- leaving the outer open-air fortress to the Uruks. A lull occurs in the battle. Gimli rallies the Rohirrim with the Deeping Horn, and Théoden leads a cavalry charge that clears the outer fortress of Uruks again. By this time, it is near daybreak. A vast forest has sprung up across the ravine, blocking the Uruks' exit. Gandalf arrives with 1,000 infantry led by Erkenbrand. The Dunlendings (number unknown) surrender immediately, while the Uruks flee into the forest. The forest is actually a vast group of savage, semi-sentient almost-Ents known as Huorns. The Hurons kill the 10,000 Uruk-hais. The Huorns are motionless by daybreak, and depart the next night -- leaving behind a vast number of dead Uruks. The Uruks are heaped up and covered over, and their grave later is known as "Death's Down".
In Peter Jackson's version -- ugh -- Théoden refuses the help of Éomer (whom he exiled while under Saruman's influence), and foolishly rides to the Hornburg with his women and children. Gandalf and Aragorn criticize the choice, arguing that Théoden is "walking into a trap". (In fact, their criticism is insanely stupid. Théoden has roughly 10,000 unarmed women, children, and old people to protect. He can't do so at Edoras. His cavalry is outnumbered on the field of battle. A defensive battle is the best he can hope for.) Suddenly, a force of several hundred Elves under the command of Haldir arrive. The 10,000 Uruk-hai attack. (No Dunlendings show up, even though in a prior scene they are shown swearing their allegiance to Saruman.) The defenders suffer heavy losses (nearly all the Elves are killed) and the Deeping Wall is topped. The breach is not bad. (Theoden asks "Is that all there is?") The Uruks attempt to breach the Hornburg door, and are repulsed by Gimli and Aragorn. The Uruks then blow a hole in the Deeping Wall, and the Rohirrim flee into the Glittering Caves. Gimli sounds the Horn of the Hornburg, and Theodon and Aragorn ride out in one last desperate charge (to their deaths, they believe). Gandalf arrives with Éomer and 2,000 Rohirrim cavlary, and they destroy the Uruks.
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Peter Jackson apparently had no real grasp of how to handle the Battle of the Hornburg.
In a late draft of the film, Arwen depicted was a warrior princess and not the willowy, frail, ethereal daughter or Elrond that she took in the finished motion picture. Jackson actually filmed scenes in which Elrond and Arwen go to see Galadriel in person and beg for her to send her troops to Rohan. She consents, and Arwen leads the Lothlórien Elves to Rohan. The script intended for Arwen to participate in the Battle of the Hornburg, and footage of Arwen fighting some Uruk-Hai was shot but was not used in the final film.
Midway through filming, Jackson decided to change the concept of Arwen to what is seen on film. But he decided to still have the Lothlórien Elves show up and help out the Rohirrim.
Jackson later realized the arrival of the Elves was not necessary. He wanted to reshoot the entire battle scene without them, and even considered using CGI to cut them out. But by this time he was out of money and out of time and had to leave them in.
For The Return of the King, Jackson began the film by showing Arwen swimming naked in a pool in Aglarond (the Glittering Caves behind Helm's Deep). Aragorn would come to her, and there would be a romantic interlude to begin things. Concept art by visual effects art director Paul Lasaine was completed, but the scene was cut from the script and nothing shot.
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As everyone by now is aware, Miramax originally agreed to finance two The Lord of the Rings films in 1995. In June 1998, with $15 million having been spent and not a single frame of film exposed, Miramax attempted to cut the budget to just a single picture. Jackson managed to win a deal from Harvey Weinstein: The project could be completed by another studio, if the studio (a) reimbursed Miramax for all funds already spent; (b) purchased the rights to all technical, concept, and script work; (c) gave the Weinsteins exeuctive producer credit on the films; and (d) gave Miramax a 5 percent cut of the gross. New Line Cinema agreed to the terms without much alteration.
The Helm's Deep/Deeping Wall/Hornburg set was designed by Alan Lee. Lee illustrated a number of scenes of the battle over the previous 25 years, so his selection to work on the Hornburg concepts was a natural. Because this set was considered the most difficult to design and build, the design for it was the first thing Lee began working on when he joined the project in November 1997. Lee's work was meant to make the Hornburg tower look like a World War I bunker. Paul Lasaine then refined Lee's concept, and it is Lasaine's design which is seen on film.
It's not clear just when Lee and Lasaine finished work on their design concept, nor when the first miniature was constructed. But Lasaine has said that a 1/35th scale miniature of the set was ready some time before June 1998 (the date New Line Cinema was brought on board to finance the films). This miniature was a true miniature, six feet wide and three feet deep, suitable only for wide shots. (By this reckoning, the Deeping Wall would be 80 feet high and 150 to 200 feet in length.) The Deeping Wall and Hornburg, as well as the fortress behind the Deeping Wall, was sculpted from polystyrene. The rock representing the mountain ravine in which the fortress was constructed was only roughly sculpted. To create a more detailed rock face, sheets of heavy, industrial tinfoil were molded to the underlying structure and then given a more finely sculpted look.
This set was used by Peter Jackson to help show Miramax executives what he intended to film. About 40,000 toy soldiers were purchased, repainted, and used to depict the Elves, Rohirrim, and Uruks as they attacked the Hornburg and Deeping Wall. Jackson would be lowered over the set on a camera crane and use a 35mm camera to swoop over the set and depict potential camera shots and movements of actors.
Later, this set was updated to be even more detailed, as it was now going to be used to close-up camera work. This required not only extensive repainting but a great deal of work on the "cut stone" rock of the Deeping Wall and the Hornburg. Ingeniously, miniature builder Mary Maclachlan designed a stamp which could mimic both light and deep cuts in stone. It was used to redetail both elements of the miniature.
For certain shots, and for the destruction of the Deeping Wall, a much larger "bigature" was needed. This model was built to 1/3 scale (some sources say 1/4 scale), with the top of the barbican giving access to the Hornburg tower about 20 feet high. As seen in the photos below, this "bigature" was so large, a person could stoop and pass through the gate into the fortress behind. Once again, due to the complexity of the model and the extensive amount of time needed to detail it to match the miniature, it was the first bigature constructed for the films.
This bigature was used primarily for shots in which the Uruks attack the Deeping Wall early in the battle. It was digitally composited with shots of Uruks below, CGI grapping hooks and ladders, and live-action shots of Elves and Rohirrim standing on a Deeping Wall set. Forced perspective was used to make the bigature look even larger: The foreground parts of the model were built larger than the middle and rear-ground parts, to trick the eye into thinking the model was larger and deeper than it really was. Action Man dolls (similar to the jointed 12-inch G.I. Joe doll) were placed on the model as it was being built to provide model-makers with a scale reference. (The doll had only been reintroduced in 1993.)
This bigature was also used to depict the explosion which destroyed the Deeping Wall. The Deeping Wall explosion was a one-time-only shot. The bigature could not be rebuilt (easily) if it failed. A number of cameras were used to capture the shot from a wide number of angles and positions, so that they could be edited together.