Service record Edit
In 2285, Kruge played a major role in a plot to obtain intelligence on the Genesis Device, a Federation technology designed to instantly terraform an entire planet. He saw it as a weapon, and sought to bring that technology to the Empire. He recruited Valkris as a spy to obtain material from the project. Successful, she made a rendezvous with Kruge on the Merchantman. Unfortunately, she was not to view the material, so Kruge destroyed the vessel without beaming her aboard.
With the project summary in hand, Kruge ordered a course set for the Genesis Planet, which had only recently been formed. Arriving at that destination, he and his crew encountered the USS Grissom, a Federation science vessel assigned to study the planet. In an attempt to gain hostages with which to bargain for the Genesis technology, Kruge ordered his gunner to target the Grissom's engines in order to disable the vessel. However, in what the gunner described as a "lucky shot," the Grissom was destroyed. Kruge responded by instantly killing the gunner. After Torg found that a landing party from the Grissom had survived on the planet's surface, Kruge led a team to search for them.
Kruge and his officers eventually located the team, consisting of Starfleet officer Lieutenant Saavik, son of Admiral James T. Kirk David Marcus, and a rejuvenated Captain Spock, whose body had been revived by the Genesis wave. Taking the team as hostages, Kruge demanded to know the secret of Genesis, and refused to believe Saavik when she informed him that the technology was fundamentally flawed, and that the planet they were on was on the verge of destroying itself. Upon the arrival of Admiral Kirk and the USS Enterprise, Kruge returned to his ship and attempted to ambush the Federation vessel. The Enterprise crew detected the Bird-of-Prey's cloaked approach and got off the first shot. Kruge returned fire, expecting to be destroyed because the Federation ship outgunned him ten to one. He was meanwhile unaware that the Enterprise was crewed only by Kirk and a handful of bridge officers. Without its normal crew of hundreds, the Enterprise was effectively disabled when Kruge's torpedo knocked out its automation center. Kirk, bluffing, opened communications to demand Kruge's surrender. Sensing that Kirk was hiding something, Kruge instead ordered Kirk's surrender, threatening to execute the prisoners as "enemies of galactic peace." As proof of his commitment, Kruge ordered his men on the surface to choose at random and kill one of the prisoners. As one of Kruge's men moved to stab Saavik, David intervened, sacrificing his own life to save her. In response, Kirk deceived Kruge into believing that he was indeed surrendering, allowing a Klingon team aboard the Enterprise while he and his own crew surreptitiously set the ship's auto-destruct and beamed down to the planet.
After the destruction of the Enterprise and the death of the bulk of Kruge's crew, Kirk contacted him from the surface, demanding to be beamed up. Kruge, however, chose to beam down himself to confront Kirk, allowing the rest of his crew to transport to the Bird-of-Prey. Engaging in a fight with Kirk amid the conflagration of the dying Genesis planet, Kruge lost his footing as the ground gave way beneath him. Kirk offered to pull Kruge up from the precipice he was hanging from, but instead of accepting Kirk's offer of mercy, he attempted to yank them both to their deaths. He failed, and was left dangling from Kirk's foot over an immense lava flow. Kirk then kicked him in the face three times, causing him to fall to his death. (Star Trek III: The Search for Spock)
Background information Edit
While the antagonists in Star Trek III were originally to have been Romulans, this character was likewise thought of as a Romulan, the unnamed commander of a Romulan Bird-of-Prey. He was depicted that way in a story treatment called Star Trek III: Return to Genesis, written by Harve Bennett and dated 16 September 1982. In that story outline, he was initially described thus: "The Commander is a handsome, swarthy man with a dignity reminiscent of the 20th Century actor Omar Sharif. Like all Romulans, he is physically similar to Vulcans, his brother race. The sharp pointed ears... the tilted brows. But unlike the more highly evolved Vulcan civilization, cool and dedicated to logic, the Romulan is of blood and passion. His mission is intelligence. He is Captain of a spy ship." At the end of the story, the Romulan commander, stranded alone on the disintegrating Genesis planet, with Kirk and his crew having commandeered the Bird-of-Prey, was contacted by Kirk and offered a chance to escape. However, he declined, choosing to be doomed together with the Genesis planet. (Star Trek: The Magazine Volume 3, Issue 8, p. 30)
Kruge wasn't named until the writing of the film's screenplay, in which he was referred to as a "Battle Commander". In the first draft of the script (dated 23 March 1983), he was initially characterized thus; "Battle Commander Kruge is tall, dark, and universally attractive. Some of that comes from his arrogance, his relative youth and, by Klingon standards, his charm. He is a deadly swashbuckler." In the revised final draft of the script (dated 7 October 1983), Kruge was instead initially described as "a Klingon War Lord of handsome but frightening presence, and relative youth." The reference to him as a "Klingon War Lord" explains why Saavik, Valkris, and his crew refer to him in the film as "my Lord." This form of address among Klingons has never been used on-screen again.
The writers had Kruge kill Valkris as a way to impart to the audience that the Klingon species was extremely ruthless. (Star Trek III: The Search for Spock audio commentary)
Ever since he first read the script for Star Trek III, Kirk actor William Shatner was impressed by the writing of the Kruge character. In the Shatner and Chris Kreski book Star Trek Movie Memories (hardcover ed., pp. 159-160), Shatner remembered, "I liked Kruge, our over-the-top gung-ho/psycho Klingon power junkie, a lot."
Prior to Christopher Lloyd being cast as Kruge, many candidates tried out for the part. (Star Trek Movie Memories, hardcover ed., p. 168; I Am Spock, hardcover ed., p. 226) Leonard Nimoy described the task of casting the role as "the biggest issue we had on III." He and Harve Bennett discussed a lot of people who might fit the part. (Star Trek Movie Memories, hardcover ed., p. 168) Nimoy and Bennett also auditioned many actors for the job, although it kept seeming as though those auditionees didn't do the role justice. (I Am Spock, hardcover ed., p. 226; Star Trek Movie Memories, hardcover ed., p. 168) Nimoy related, "When they read the part, it just didn't seem to come to life. It didn't work. They just couldn't grasp the character somehow." (Star Trek Movie Memories, hardcover ed., p. 168) The performers who auditioned for the role included Edward James Olmos, of Battlestar Galactica fame. 
Christopher Lloyd also came in to be interviewed for the job. (Star Trek III: The Search for Spock audio commentary) Since Lloyd wasn't yet established as a major movie actor, it wasn't a forgone conclusion that he would win the part. There was even some worry at the studio that Lloyd lacked the performance skills to portray Kruge, as he was used to appearing in a regular comedic role in series television and the studio wasn't sure if he could play a far different character. "There was some concern [....] Could he be this commanding authority figure that Kruge had to be?" recalled Leonard Nimoy. (Star Trek: The Magazine Volume 3, Issue 8, pp. 17-18) Even though Nimoy had admired Lloyd for years prior to the making of Star Trek III, the audition amazed Nimoy. "What he really did for me when he came in," Nimoy stated about Lloyd, "was show me how totally chameleon-like he is. When he came in and read this role, he was totally unlike anything I'd ever seen him do before, and I was just swept away by his ability to transform himself so completely and to give us this wonderful, powerful character, and I went to bat to hire him on the spot." (Star Trek III: The Search for Spock audio commentary)
When the part was offered to Christopher Lloyd, Lloyd himself was extremely surprised. "I was honored. Really, I was tickled and delighted," he reminisced. "What can I say? I felt like I was becoming part of a special club." (Starlog, issue 82, p. 20) Describing Kruge years after playing him, Lloyd said, "It's a role that I thoroughly enjoyed. It was fun to play an evil character that has no remorse about anything he does [....] I didn't quite know what about me they saw from previous work that convinced them that maybe I'd be a good Klingon. But I love doing that kind of thing, a far-out character."  Lloyd speculated that, by casting him in the role, "they just played a hunch, I guess." Regarding Kruge's villainy, he elaborated, "I mean, he epitomizes somebody with absolutely no moral conscience. He even blows up his so-called girlfriend in another spaceship. They have a short conversation at the beginning, and he doesn't even apologize. She's amenable because… well, it's for whatever political reasons. But, yeah, he's just evil [....] He's demonic. There's no conscience in place at any point, and he has no apologies for any of his actions. He just goes out and destroys and kills and creates havoc until he gets what he wants. And that was fun to play. I loved all the makeup and the clothes, the whole Klingon look. It was a joy." 
The role of Kruge challenged Christopher Lloyd to learn Klingonese. He struggled to learn the language, but, with Leonard Nimoy's help, Lloyd endeavored to make Kruge's uses of Klingonese as accurate as possible. (Starlog, issue 82, p. 21)
As the director of Star Trek III, Leonard Nimoy tried to accentuate how menacing Kruge looked, such as by using tight angles on the bridge of his Bird-of-Prey. Although Nimoy tried to use that method for the ship's Klingon crew in general, he was especially mindful of it in relation to their commander. "And the fact that he was elevated above them in the way he was gave him a certain amount of ominous power," Nimoy pointed out. (Star Trek: The Magazine Volume 3, Issue 8, p. 16)
Although Christopher Lloyd and Chekov actor Walter Koenig had been schoolmates in their childhood, Koenig found that, during the making of Star Trek III, Lloyd's focus on playing Kruge took priority. "He was very much into his character, which was good, but he was not very approachable as a consequence," Koenig noted. Eddie Egan, who was working in the publicity department at Paramount Pictures when the film was being marketed, recollected about Lloyd, "I think he just felt very out of place. There were whole parts in the movie where he didn't interact with any of them until the end except with Robin Curtis and Merritt Butrick [who played Saavik and David Marcus respectively]. No one likes wearing that kind of makeup in that kind of heat for that many hours a day. It was a very quick job. He didn't work that long." Deborah Arakelian, assistant to Harve Bennett, remembered, "Chris Lloyd stayed to himself. He would sit there in full makeup with his little wire glasses on reading the trades [....] It was pretty funny to look at. He had almost no interaction with anyone. Came in and did his job, such a professional." (The Fifty-Year Mission: The First 25 Years)
Upon considering how to film the scene in which Kruge is attacked by massive worms, the production crew were careful not to ruin Kruge's make-up. This prohibited them from doing multiple takes of the worms leaping on him, as the film crew were anxious that shooting too many takes would eventually mess up the prosthetics Christopher Lloyd needed to wear for the role. Even so, during the actual filming, his elaborate Klingon costume kept snagging on fishing line that the team used to make the rubber worms appear to be moving. For a close-up insert shot of Kruge grabbing onto one of the worms, Industrial Light & Magic effects cameraman Don Dow stood in for Lloyd and the shot was captured at ILM. (Cinefex, No. 18, pp. 55 & 56)
To portray Kruge's fall from a precipice on the Genesis Planet, a stuntman dressed as Kruge was filmed taking a short drop into an airbag. At ILM, David Sosalla and Tom St. Armand were called upon to enact Kruge's final fate. In Sosalla's opinion, Kruge tumbling to his death made him seem "sort of like Wile E. Coyote." The shot was to be completed with an articulated stop-motion puppet visually substituting the stuntman, seemlessly, midway through the plunge. However, the live-action footage complicated the puppet's requirements. "The problem was that the cut we were given of Kruge going over the cliff was so short that at the end of it he was still large in the frame," explained Sosalla. "We had to meticulously copy the images, picking up where Kruge is kicked off, and still have it hold up under scrutiny of being half-size on screen. That's pretty hard for a little puppet." The puppet was sculpted by Sosalla and crafted by Sean Casey. It was fitted over a special armature, which Armand designed. The puppet's movements were programmed by Denis Muren, with Armand animating the puppet when it was filmed against bluescreen. "It wasn't a huge puppet, but it held up magnificently under close scrutiny," Sosalla remarked. (Cinefex, No. 18, p. 63 & 64) Christopher Lloyd was similarly proud of how Kruge's demise was ultimately depicted, the actor enthusing, "I thought it was a great ending for the character, very entertaining. And I couldn't tell where I ended and the puppet started." 
Christopher Lloyd was hopeful that his performance of Kruge would be popular. Shortly before Star Trek III, he proclaimed, "I like to think that whatever I did in the film fulfills the Trekkian hopes. Know what I mean? I'm thrilled thinking that somehow I've contributed to the whole Trekkian mystique." (Starlog, issue 82, p. 20) Leonard Nimoy found that Lloyd was very helpful in making Kruge seem larger than life; in Nimoy's opinion, Lloyd played the role "brilliantly," defying the studio concerns that he wouldn't be capable of the assignment. (Star Trek III: The Search for Spock audio commentary; Star Trek: The Magazine Volume 3, Issue 8, p. 18) "I thought he brought a tremendous amount of theatricality to the character of the Klingon," Nimoy opined. (Star Trek III: The Search for Spock audio commentary) Nimoy elaborated, "His portrayal of Kruge was a joy to watch; he literally smacked his lips as though savoring the role. It made me happier than ever to be working with Klingons!" (I Am Spock, hardcover ed., p. 226) William Shatner also approved of how Lloyd played the role, saying the actor strengthened the principal cast. "Hidden under gobs of makeup and one of those patented Klingon headpieces that always look sort of like big bronze omelets, Lloyd was almost entirely unrecognizable [...] and he chewed the scenery with a tremendous amount of skill and enthusiasm (even going so far as to become fluent in the formal Klingonese language) [....] He quickly grew more comfortable [...] in his role," observed Shatner and Chris Kreski. (Star Trek Movie Memories, hardcover ed., pp. 173-174) On the other hand, David A. Goodman critiqued, "I thought Christopher Lloyd didn't feel like a Klingon to me." (The Fifty-Year Mission: The First 25 Years)
Kruge was the second Klingon to try and seize control of the Enterprise (the first was Kang in "Day of the Dove"). As noted in the text commentary for Star Trek III, Kruge was also the second Klingon to use hostages to coerce Kirk (that precedent was set by Kor threatening to exterminate scores of Organians in "Errand of Mercy"), and the second Klingon to fall for Kirk's bluffs (preceded by Kang doing so in "Day of the Dove").
Concerning a moment in the film when Kruge threatens Saavik with torture, Michael and Denise Okuda postulated, in the text commentary for Star Trek III, "Kruge seems unaware that Vulcans discipline themselves to control pain." Because sandwich boxes were used to decorate the base of Kruge's command chair, the commentary joked, "He had to step carefully to avoid crushing them!"
The scene in which Kruge falls to his demise was shown during a video montage at the end of the Star Trek 25th Anniversary Special, followed by the text "He Boldly Went Where No One Went Before."
A Klingon named Kruge appears in the novel Faces of Fire by Michael Jan Friedman, which takes place several years before the events of Star Trek III: The Search for Spock. It is unclear whether he is the same character as appears in the movie, but the two are strongly similar.