Day of the Dove (episode)
An extremely powerful non-corporeal being brings the Enterprise and a Klingon ship in direct conflict with one another.

Summary

Teaser 

Responding to a distress call from Beta XII-A, a landing party from the  beams down to the planet. The team consists of Captain Kirk, Doctor McCoy, Ensign Chekov, and Lieutenant , a security officer. They find no trace that there ever was a human colony on the planet, nor any indication of any attack. Dr. McCoy reminds Kirk that whoever sent the distress call claimed they were under attack by an unidentified starship. From the bridge of the orbiting Enterprise, Spock hails the captain and reports that a Klingon battle cruiser is approaching. Although Kirk authorizes the Vulcan to defend the Starfleet ship, Lieutenant Sulu determines that the Klingon vessel is totally disabled, but the Enterprise never fired upon it. A team of Klingons beams to the planet and approaches the Starfleet officers. Commander Kang, the leader of the team, believes that Kirk is responsible for the damage to his ship and for killing four hundred members of his crew. He smacks Kirk in the face with his disruptor, knocking Kirk to the ground. As a result, the Klingon claims the Enterprise as his own and takes the Enterprise crew as prisoners of the Klingons. Both men are unaware of a strange ball of light nearby, which is in fact a non-corporeal lifeform.

Act One 

Kang tells Kirk that the Klingons have honored a peace treaty "to the letter" with the Federation for the past three years, and that Kirk appears to have tested a new weapon against his ship, killing his crew. Kirk rebuts that the Federation colony on the planet was destroyed. But Kang scoffs at this, saying there is no evidence of bodies or ruins. Kirk says this is because it was a new Klingon weapon that leaves no traces, and that the Federation does not conduct sneak attacks. 

Kang threatens to torture one of the Starfleet prisoners, but has difficulty deciding which officer will suffer – until Chekov angrily cries out that the Klingons killed his brother, Piotr Chekov, on a Federation research outpost on Archanis IV. One of the Klingons uses an agonizer to inflict pain on Chekov. After much debating with Kang, Kirk authorizes Spock to beam the Klingon and Starfleet officers aboard the Enterprise; however, while giving the order Kirk also presses a distress key on his communicator, causing an amber light to blink on the command chair. Seeing the signal, Spock orders that the landing party be beamed into the ship's transporter room, but he also has the Klingons suspended in the pattern buffer and they are arrested by Enterprise security when they are rematerialized.

As the Klingon battle cruiser is emitting an excessive amount of harmful radiation, Kirk intends to destroy the alien craft. Klingon survivors are beamed aboard, including Mara – Kang's wife and science officer. Mara fears that she will be tortured for their scientific and military information, but Kirk assures her and her husband that the Klingons will not be harmed. The captain orders Lieutenant Johnson to secure the Klingon prisoners in the crew lounge and to program the food synthesizer for Klingon cuisine. Spock explains that when the Enterprise received the distress call, the Klingons were too far away to have been the attackers. McCoy argues that they know the Klingons did attack, and that the log tapes will prove the innocence of the Enterprise. 

The Enterprise is unable to contact Starfleet Command, as all subspace frequencies are being blocked. The Enterprise destroys the Klingon craft with its forward phasers in orbit of the planet, but communication with Starfleet is still unobtainable.

In the crew lounge, Kang plans Kirk's death, vowing to hang Kirk's head on a wall in his quarters. Mara fears that the Starfleet crew will overpower the Klingons, while another Klingon officer eagerly advises Kang that they should strike quickly. Kang tells the officer to be patient and opines that the Starfleet crew will make a mistake soon and they will seize upon it.

Meanwhile, the crew loses control of the Enterprise and several malfunctions result in the ship pursuing a new course out of the the galaxy. Scott explains that controls have gone crazy, and engines have gone to warp 9 by themselves. Nearly four hundred crewmen are trapped by emergency bulkheads on the vessel's lower decks. Assuming that the Klingons are responsible, Kirk questions Kang in the crew lounge. Kang denies any responsibility. Kirk tells Kang that before he puts him in the brig, there is something he "owes him" and punches Kang for having struck him earlier on Beta XII-A. Suddenly, several inanimate objects in the room, including a three-dimensional chess set, transform into swords. Kirk orders his men to draw phasers, which also mysteriously transform into swords.

Act Two 
The Starfleet officers and the Klingons fight, using these primitive weapons of their ancestors. Two more security officers join the battle against the Klingons and Johnson is injured in the fight. The crew members luckily escape in a turbolift that takes Johnson and the other security personnel to sickbay. With the Klingons free to roam the ship, Kirk stays in the turbolift and heads to the bridge. There, he informs the senior staff of the situation. The captain contacts Scott in engineering and tells him that he must free the trapped crewmen at all costs so they may help to fight the Klingons. The engineer reports that he has been unable to regain control of the ship's velocity and is amazed that the vessel has not yet torn itself apart.

Spock deduces that the Klingons could not have caused the swords to appear, as the instantaneous transmutation of matter that caused their creation is beyond the capabilities of Klingon technology. Furthermore, Spock reasons, if the Klingons had this power, they would have created more effective weapons than just swords – and only for themselves.

When Kirk orders Sulu to take control of engineering and the auxiliary control center, Chekov insists that he join the helmsman. He and Kirk raise swords against each other. Despite Kirk's direct order to return to his post, Chekov explains that he must avenge the murder of his brother and dives into the turbolift aft of the bridge. With a puzzled expression, Sulu tells Kirk that Chekov is an only child and never had any such brother.

In sickbay, McCoy grows furious with the Klingons, calling them "filthy butchers" as he treats an injured crew member with a numanol capsule. A group of Klingons enters the auxiliary control center and accesses the Enterprises specifications. When Mara notifies Kang that there are as many Starfleet officers as there are Klingons aboard the ship, Kang decides to make an attempt at commandeering the vessel and plans to take control of engineering first.

In the armory, Scott uses a communicator to contact the bridge and reports to Kirk that the phaser torches have proven useless against the metal bulkheads that have trapped the crewmen, as something has happened to the metal. The armory itself now contains only antique weaponry. Scott marvels at the beauty of a claymore sword, and refuses Kirk's orders to return to engineering. Scott and the Starfleet personnel in engineering are attacked by Klingon soldiers, who drive them out, and seize control of the engine room.

On the bridge, Spock detects a single alien life force – the ball of light from Beta XII-A. Spock consults the ship's computer, which reveals that the entity is composed of pure energy, has intelligence and is acting toward an unknown purpose. 

When Spock points out that if Chekov's memory was manipulated to create an imaginary brother then so could theirs have been, Kirk realizes that the alien force is also responsible for the distress call from a colony that also never existed, as well as the creation of the antique weapons aboard the ship. He proposes to form a truce with Kang, but Spock reminds the captain that the Klingons are infamous for refusing to agree to a truce once blood is drawn. When McCoy enters the bridge, he is overly outraged by the fact that the senior officers are considering a truce with the fiendish Klingons, who would force them into "slave labor, death planets, experiments" Spock informs the doctor of the alien's presence and Kirk adds that the alien is their real enemy, but McCoy believes that they must obliterate the Klingons in what he calls a "fight to the death."

After the doctor angrily exits the room, Kang hails the bridge. The Klingon notifies Kirk that his soldiers have captured the engineering section of the ship. Kang is now in control of the Enterprises power and life support systems. The Klingon warns Kirk that he will "die of suffocation in the icy cold of space." The bridge lights darken.

Act Three 
As the Enterprise rushes through space at warp factor nine, Kirk uses a tricorder to record a log entry.

"The Enterprise is heading out of our galaxy, controlled by a mysterious alien somewhere aboard the ship. Engineering has been taken over by Klingons who have cut off life support systems."

With Kirk's authorization, Sulu leaves to protect the life support circuits and auxiliary power in emergency manual control. Scott enters, irrationally desperate to fight the Klingons. Influenced by the alien entity, the engineer trades insults with Spock. Kirk stops Spock moments before the Vulcan can assault Scott with his fist, but begins to insult the science officer himself. The captain gradually realizes that he and his two officers are being manipulated by the entity. He wonders why the alien seems to be staging a war between his crew and the Klingons. Spock notes the importance of finding the entity, determining its motives, and stopping it from causing any further hostilities.

From a Jefferies tube, Sulu reports that systems should be functioning but are not responding. Suddenly, power and life support are restored but the helmsman claims he was not responsible for the restoration.

Aware of the sudden change, Mara notifies Kang that sensors show life support holding steady. She reports that she is neither able to cause it to falter nor deviate the ship from its course toward the Klingon Empire. Kang angrily ponders the nature of the power that supports his men in battle but stops them from achieving victory. Under Kang's orders, Mara leaves engineering with another Klingon officer and heads to the ship's main life support couplings on deck 6.

As the alien continues to creep through the Enterprise, Spock detects the entity using the ship's newly reactivated sensors. He and Kirk exit the bridge and take a turbolift toward the engineering section, where the anomaly is hiding.

Meanwhile, Chekov unknowingly follows the alien through a corridor. When he hears a door open and close behind him, Chekov hides in an alcove. He attacks Mara and the Klingon officer accompanying her as they pass by. After the officer falls to the deck unconscious, Chekov decides to rape Mara, but is stopped by Kirk when he arrives with Spock. Kirk slaps Chekov several times, but Spock reminds him that Chekov was not in control of himself. Chekov's body slumps to the ground. Although Kirk tries to explain the situation to Mara and pleads for a temporary truce, she does not respond. Spock takes her away securely while Kirk follows close behind, carrying Chekov in his arms.

In sickbay, McCoy scans Chekov's brainwaves and determines that he was suffering from paranoid mania. The doctor also tells Kirk that several officers, including Johnson, have suffered serious injuries that are healing at a miraculously accelerated rate. Spock deduces that the alien wants the officers to stay alive. As he and the doctor discuss the entity, Johnson regains consciousness unobserved. The lieutenant watches as Kirk, Spock and Mara leave in search of the alien.

Soon, Kirk and his two companions discover the anomaly. Lieutenant Johnson suddenly appears behind Kirk and reports that he is ready for duty. The captain instructs Johnson to return to sickbay, but the lieutenant insanely shouts that he has orders to kill the Klingons. He attacks Kirk with a sword, though he loses consciousness again when Spock employs the Vulcan nerve pinch from behind him.

Kirk and Spock observe that the alien's life energy momentarily increased during Johnson's emotional outburst. This leads the officers to suspect that the entity thrives on the hateful emotions of others. To combat the alien, Kirk and Spock agree that they must join forces with the Klingons and eliminate all hateful emotions from the ship. The captain uses an intercom to contact Kang, but Mara rushes forward and warns the Klingon commander that Kirk has set a trap.

As Kang's mind is being affected by the entity, he refuses to answer any further hails. Scott contacts Kirk from the bridge, informing the captain that the ship's dilithium crystals are deteriorating and will be completely depleted in twelve minutes. With the crew's losing their minds to the alien seemingly inevitable, and with the ship about to be drifting powerless in space, Kirk asks Mara if she now believes that the entity exists.

Act Four 
"Captain's log, stardate… Armageddon. We must find a way to defeat the alien force of hate that has taken over the Enterprise, stop the war now, or spend eternity in futile, bloody violence."

Holding Mara's arm, Kirk accompanies Spock out of a turbolift and onto the bridge. The ship's dilithium crystals are still being drained and, according to Spock, will be totally depleted in less than ten minutes. Scott and the science officer recommend using Mara to force Kang into agreeing to a truce. Kirk contacts Kang and carries out the suggestion, threatening the Klingon commander that Mara will be killed in five seconds if he does not reply. But Kang simply accepts that his wife is a victim of war. After closing the communications channel to Kang, Kirk assures Mara that the Federation does not kill its prisoners – she has been listening to propaganda and fables.

Mara realizes that the alien entity actually exists. Scott tells her that the Klingons are also under alien power and that a truce would save both the Klingons and Humans aboard the Enterprise. However, Mara insists that her people must continue to hunt and fight in order to survive. When Kirk tells her that mutual trust and assistance can also help a civilization endure, Mara agrees to help the captain and take him to Kang.

With less than nine minutes before the ship loses power, Kirk decides to use intraship beaming to transport through the Klingon defenses and reach Kang. The process is extremely dangerous but the captain chooses to take the risk. Kirk and Mara dematerialize from the ship's transporter room into engineering.

Against Mara's objections, Kirk and Kang fight each other. Outside engineering, a team of Starfleet security officers led by Spock and McCoy battle several Klingons. The senior officers leave the confrontation and enter engineering. They watch as Kirk surrenders and finally manages to persuade Kang that they are all being controlled by an alien. Eventually, the Klingon commander purposefully drops his sword. He and Kirk use the ship-wide intercom to direct their respective troops to cease hostilities. When the officers comply, the entity is weakened by the abrupt termination of violence.

Spock suggests that "good spirits" would further weaken the alien. Calling it a "dead duck", Kirk urges it to leave the ship. Kang tells the entity that Klingons need no urging to hate Humans and also yells at it to leave the Enterprise, as they have no wish to fight "in a burning house". Kirk shares a hearty laugh with McCoy and Kang, and the alien finally departs from the Enterprise into open space.

Log entries 
 Captain's log, USS Enterprise (NCC-1701), 2268

Memorable quotes 
"I don't propose to spend the rest of my life on this ball of dust arguing your fantasies! The Enterprise is mine!! Instruct your transporter room to beam us aboard."
"Go to the devil."
"We have no devil, Kirk. But we understand the habits of yours. I shall torture you to death, one by one, until your noble Captain cries, 'Enough'. Who will be first?"
 Kang and James T. Kirk, after Kang claims Kirk's crew as his prisoners – 

"Cossacks! Filthy Klingon murderers!! You killed my brother, Piotr! The Archanis IV research outpost! A hundred peaceful people massacred!! Just like you did here! My brother! You killed my brother!"
"And you volunteer to join him. That is loyalty."
 - Chekov and Kang, before Kang tortures him – 

"Four thousand throats may be cut in one night by a running man."
 - Kang's Officer, quoting a Klingon proverb to Mara

"Most interesting. The bulk of your crew trapped? Your ship racing from this galaxy at wild speeds? Delightful."
 - Kang, to Kirk

"There are rules, even in war. You don't keep hacking at a man after he's down!"
 - McCoy, after treating Johnson

"Keep your Vulcan hands off me! Just keep away! Your feelings might be hurt, you green-blooded half-breed!"
"May I say that I have not thoroughly enjoyed serving with Humans. I find their illogic and foolish emotions a constant irritant."
"Then transfer out, freak!"
 - Scott and Spock, before they grapple with one another – 

"Has a war been staged for us? Complete with weapons and ideology and patriotic drum beating?"
 - Kirk to Spock, on their Klingon battle

"You're not Human, but you're very beautiful. Very beautiful."
 - Chekov, before he tries to rape Mara

"I, too, felt a brief surge of racial bigotry. Most distasteful."
 - Spock, to McCoy 

"The Federation doesn't kill or mistreat its prisoners. You've been listening to propaganda … fables."
 - Kirk to Mara, after Kang calls his bluff

"We have always fought. We must. We are hunters, captain, tracking and taking what we need."
 - Mara, on the Klingon way of life

"Those who hate and fight must stop themselves, doctor. Otherwise, it is not stopped."
 - Spock, during Kirk and Kang's swordfight

"Klingons kill for their own purposes."
 - Kang, tossing away his sword

"Get off my ship! You're a dead duck here. You're powerless. We know about you, and we don't want to play. Maybe… maybe there are others like you around. Maybe you've caused a lot of suffering, a lot of history, but that's all over. We'll be on guard now. We'll be ready for you, so ship out! Come on, haul it!"
"Yeah, out already!"
"Out! We need no urging to hate Humans. But for the present, only a fool fights in a burning house. Out!!"
 - James T. Kirk, Leonard McCoy and Kang to the entity, with the latter quoting a Klingon proverb –

Background information

Title, story, and production 
 This episode had the working title "For They Shall Inherit".
 John Colicos was originally going to return as Commander Kor for this episode. A feature film commitment (most probably Anne of a Thousand Days, starring Geneviève Bujold) made this impossible.   Had the episode featured Kor, it would've been essentially a reversal of their conflict in .  In that episode, the two sides fought of their own accord and were stopped (rather than pushed to fight further) by non-corporeal beings.
 Jerome Bixby's original story featured the Enterprise receiving a false distress call from a Federation colony, while en route to celebrate "Peace Day" (anniversary of the day the nations of Earth finally made peace with each other). Arriving to the planet, the crew, along with the crew of a Klingon vessel, also lured there with a fake distress signal, are captured by an alien race and forced to compete against each other in bloody duels. The aliens, appearing to be humanoid, turn out to be, in reality, energy beings consisting of "a blob of light", feeding off the aggression of the two enemy crews. Finally, Kirk and the Klingon commander realize they need to work together and make peace with each other, so the aliens won't get violence to feed on. Eventually, the Klingons and the Enterprise crew sing songs and have a peace march together. (These Are the Voyages: TOS Season Three)
 The production staff convinced Bixby that such exaggeration as the "peace march" was not necessary to understand the message of the episode. 
 This story bore a resemblance to several earlier produced episodes: the Enterprise crew captured by powerful aliens on the surface of a planet (, , ), humanoid aliens turning out to be "blobs of light" (), crewmembers forced to take part in deadly gladiatorial combat (, , ), and even featured Kirk trying to seduce a member of the alien race (appearing to be a beautiful woman) as an escape tactic (similarly to ).  Another (possible) reference to a previous episode might be , which also had an antagonistic, non-corproreal, alien which fed on strong emotion (in that case, fear)
 Marvin Chomsky filmed this episode in five and a half days, making him the only director besides Marc Daniels (who shot "The Menagerie" in five and a half days, and  in five days) to finish an episode in less time than the usually alloted six production days. (Joseph Pevney also finished , which was expected to stretch to seven days, in only six.)

Continuity 
 Michael Ansara reprised his role as Kang in the  episode  and the  episode .
 This episode marks the only appearance in the original series of female Klingons. 
 Although intraship beaming is routine in later incarnations of 'Star Trek' (often in the form of "site-to-site transport"), this is the first and only time it is done in the original series.
 The Klingon who says, "Stand and fight, you cowards!" is Pete Kellett, who previously appeared in  as , Kirk's henchman but was uncredited for this role despite speaking.

 This is the only time Sulu is seen in engineering or working in a Jefferies tube.
 This episode affords a third and final glimpse of the "working" communicator's central spinning moiré disc, which was controlled by an inner stopwatch mechanism. Its first appearance was in , and its second appearance was in .
 The Klingon agonizer used on Chekov is the same one seen in .
 When the entity exits the Enterprise at the end of the episode, it is seen leaving through the front center of the secondary hull, thus canonizing the location of main engineering in a Constitution-class starship for the first time.
 Footage of the Klingon ship is reused from  which originally aired after this episode.
 The footage of engineering, with the hovering entity, was recycled from , which featured a floating Kirk in place of the entity.
 It is established that Kang's cruiser carried a crew of 400+ when he says "four hundred of my crew dead". The actual complement may be closer to 440 because Mara says there were "forty [Klingon survivors] against four hundred of them [Enterprise crew]".
 The officers' quarters are apparently in the saucer section, possibly Deck 6, as seen when the entity moves through circular corridors and passes a sign that says "Officers Quarters 6F-38". Kang and his shipmates also seem to be detained on this deck because Kirk orders them to be held not in the brig but in the officer's lounge. Also, if the turbolift "deck indicator" can be believed, there were about 6 decks between the bridge and this floor, with sickbay being in-between at around deck 5 or 4. All of the action in the episode seems to happen at no lower than deck 7, which is squarely in the primary saucer hull, and this includes engineering, auxiliary control, and the armory. 
 Spock says the Klingons control deck 6 and starboard deck 7, while they control everything above. At the time, the Enterprises crew controlled engineering, which means engineering must be on either port deck 7 or anywhere from deck 5 and up. However, in the next scene, Scott comes up a ladder shaft and walks through the nearby doors into the "Engineering Section" which is clearly marked by a sign on the wall. This means engineering cannot be on "port deck 7" but anywhere from deck 5 and up, again placing engineering squarely in the saucer.
 There is also a room or area called "emergency manual control" which seems to be the famous "Jefferies tube", because Kirk orders Sulu to go down there and we next see Sulu standing in it fiddling with switches.
 The "main life support couplings" are on deck 6, as Mara says, and this is where she goes when she is confronted by Chekov. 
 Spock says "reactor number three" is near engineering, and both are next to a curved corridor, again indicating saucer location for engineering. The entity moves from this curved corridor into engineering, and in the next scene emerges again into the curved corridor, which seems to be deck 6 because Mara has come to fiddle with the "main life support couplings". Mara and her escort seem to have slipped out of the red door to their left, which seems to be the door to engineering, which they just left Kang in. All of this points to a deck 6 location for engineering. It should be noted that the room itself is so tall it occupies two decks, so the upper part could be in the "hump" of the upper part of the saucer, which is deck 5.
 Kang states that the Federation and the Klingon Empire had been at peace for three years prior to this episode, evidently referring to the Treaty of Organia from . However, based on the widely accepted chronology for the original series, this treaty would have just been signed the previous year. He could have meant the amount of time in Klingon years.
 Kirk and Kang already seem to know one another. Kang uses the captain's name in the teaser; Kirk uses the Klingon commander's name at the beginning of Act One. This may have been due to Kor's having originally been written as the Klingon commander for this episode.
 This is the first time it is mentioned that Klingons still use bladed weapons, as why Kirk believes that they are behind the appearance of the swords; in all other series, this becomes a universal fact about them.
 Uhura  is seen talking to Kirk while holding a "Sgian-dubh" (Scottish knife)
 The swords are designed to the ethnic background of the users:
Kirk 18th century Navy cutlass.
Chekov a Cossack broadsword
Scott a Scottish claymore
Sulu a Japanese katana
Klingons and Enterprise Crewmen use Roman gladius with a least one mace, a medieval broadsword, and a scimitar.
 This is the only time in the original version of the original series that a Klingon warship is destroyed on screen. In the remastered version, it is also seen in the beginning of .
 The Enterprise's turbolifts are given an unusual treatment in the scene in which Chekov flees the bridge. We see him run into the turbolift at speed and bear left; the effect is of him exiting down a corridor (otherwise he'd instantly run into the wall of the turbolift car). A few moments later, after pointing out that Chekov has no brother, Sulu enters the same turbolift chamber, but bears right, again giving the impression of exiting via a corridor rather than a turbolift car. In the next scene we see Chekov's turbolift arrive at its destination, indicating that a second car had arrived to ferry Sulu.

Reception 
 Tor.com gave this episode a "warp 4" rating out 6. 
 Reviewer Dayton Ward of tor.com called the Chekov attempt-at-rape scene "arguably one of the more disturbing scenes from all of the original series."
 Reviewer William B from "Jammer's Review" had a much more positive outlook on the episode. He argued that the episode is a metaphor for man's aggression as the default. He wrote that this episode "represents the human aggressive impulse as a rule. When people get enraged, and when they get trained to fight, eventually fighting and the hatred of one's enemy becomes habitual. Its reason for existing is pretty clear – as animals, competing for resources, fighting was a matter of survival, and emotional/instinctual charge to fight and continue fighting would help survive. But taken out of its proper context, this can "take over" otherwise rational people entirely, as happens here with the human and Klingon crews, unless they can correctly identify and fight against this impulse. People are responsible for their actions – but the things carried out by fighters in the frenzy of war are so often so far from what those same people do in peacetime, that it is clear that it is sometimes difficult to keep perspective when in the emotional thrall of combat mentality. The way the creature ramps up aggressive and vengeful impulses, to the point of having Chekov nearly rape the Klingon science officer (!!!), represents this well."

Apocrypha 
 Bantam Books published a series of novelizations called "foto-novels," which took photographic stills from actual episodes and arranged word balloons and text over them, to create a  formatted story. The tenth installment was an adaptation of this episode. It includes a brief interview with Michael Ansara.
 "Blood Reign O'er Me", the fourth installment of the IDW Comics series Star Trek: Klingons - Blood Will Tell, tells the story of this episode from the Klingon perspective, and shows it to have indirectly played a very significant role in the Klingon/Federation peace process – the main character, Kahnrah, who holds the tie-breaking vote on the High council, makes the decision to support Gorkon's proposal after being told by one of Kang's men of the honor with which the Enterprise crew fought.
 In the  series of novels by Greg Cox, the Beta XII-A entity is revealed to be part of a group that Q fell in with centuries ago. This group also included the  found on , Gorgan, and the group's leader 0.

Production timeline 
 Story outline by Jerome Bixby, titled "For They Shall Inherit", 
 Revised story outline, titled "Day of the Dove", 
 Second revised story outline, 
 Third revised story outline, 
 Fourth revised story outline by Fred Freiberger, 
 First draft teleplay by Bixby, 
 Second draft teleplay, 
 Final draft teleplay by Arthur Singer, 
 Revised final draft teleplay by Freiberger, 
 Additional page revisions by Freiberger, , , 
 Filmed,  – 
 Day 1 – , Thursday (Half Day) – Desilu Stage 9: Int. Bridge
 Day 2 – , Friday – Desilu Stage 9: Int. Bridge
 Day 3 – , Monday – Desilu Stage 10: Ext. Planet surface; Desilu Stage 9: Int. Transporter room
 Day 4 – , Tuesday – Desilu Stage 9: Int. Corridors, Sickbay
 Day 5 – , Wednesday – Desilu Stage 9: Int. Sickbay,Corridors, Turbolift, Engineering, Bridge
 Day 6 – , Thursday – Desilu Stage 9: Int. Sickbay,Engineering, Bridge, Corridors, Armory, Jefferies tube, Recreation room (redress of Briefing room)
 Original airdate,  
 Rerun airdate, 
 First UK airdate, 

During the syndication run of Star Trek, no syndication cuts were made to this episode.

Video and DVD releases 
Original US Betamax release: 
 UK VHS release (two-episode tapes, CIC Video): Volume 34, catalog number VHR 2430, 
 US VHS release: 
 UK re-release (three-episode tapes, CIC Video): Volume 3.4, 
 Original US DVD release (single-disc): Volume 33, 
 As part of the TOS Season 3 DVD collection
 As part of the TOS-R Season 3 DVD collection

Links and references

Starring 
 William Shatner as Kirk

Also starring 
 Leonard Nimoy as Mr. Spock

And
 DeForest Kelley as Dr. McCoy

Guest star 
 Michael Ansara as Kang

Co-starring 
 Susan Howard as Mara
 James Doohan as Scott
 Walter Koenig as Chekov
 George Takei as Sulu
 Nichelle Nichols as Uhura
 David L. Ross as Lt. 
 Mark Tobin as a Klingon

Uncredited co-stars 
 Phil Adams as a Klingon crewman
 Majel Barrett as Computer Voice
 Richard Geary as a Enterprise security guard
 Eddie Hice as a Enterprise security guard
 Roger Holloway as Roger Lemli
 Jay Jones as a Klingon crewman
 Pete Kellett as a Klingon crewman
 Hubie Kerns, Sr. as a Klingon crewman
 Jeannie Malone as Enterprise yeoman
 Victor Paul as a Klingon crewman
 Charles Picerni as a Enterprise security lieutenant
 George Sawaya as a Klingon crewman
 David Sharpe as a Enterprise security guard
 Unknown actors as
 Enterprise orderly
 Enterprise security guard
 Enterprise security guard
 Enterprise security guard
 Klingon crewmen 1, 2, 3, 4, 5, 7, 8, and 9
 Unknown actress as Klingon crew woman

Stunts 
 Al Cavens

References 
2265; acceleration; act of war; alien; alternative; ambush (aka sneak attack); analysis; animal; answer; antique; Archanis IV Research Outpost (Archanis IV); area; armory; atmosphere; attacker; automatic transporter setting; auxiliary control center; auxiliary navigation; auxiliary power; bad guy; balance of power; ball; battle cruiser, Klingon; beast; beauty; beings that feed on emotion; Beta XII-A; Beta XII-A entity;  Beta XII-A sector; Beta XII-A ship; Beta XII-A sun; Beta Leonis Minoris; bigotry; blood; bluff; body; brain waves; brig; "bury the hatchet"; butcher; cabin; candidate; ; casualty; choice; channel; ; claymore; coliseum; colony; Commander; computation; condition red; Constitution-class decks; contact; Cossack; course; coward; crew lounge; crowd; cutlass; danger; ; "dead duck" (duck); death; death camp; death planet; deck; deflectors; devil; dilithium crystal; diplomacy; distress call; drifting; door; drum; dueling tradition; emergency bulkhead; emergency manual control; emotion; emotional outburst; enemy; energy; engineering (engineering section); engine control; engine power; entity; eternity; event; "even the score"; evidence; explosion; fable; fantasy; Federation; feeling; five-minute report; food-synthesizer; fool; freak; game; general quarters; gladius; goon; "go to the devil"; grave; green; guest; habit; half-breed; hatchet; hatred; hazard; head; healing; heart; history; hostage; hostility; house; Human; ; ice; ideology; imaginary; innocence; intelligence; intention; intercom; intraship beaming; job; ; katana; Klingons; Klingon Empire; Klingon food; knowledge; landing party; liar; library computer; lie; life; life energy level; life-energy unit; life force; life support circuits; life support couplings; life support systems; location; logic; log tape; long sword; loyalty; lust; magnification; massacre; matter; memory; metal; military men; Milky Way Galaxy; mind; minute; mistake; monster; motive; murder; murderer; "nailed down"; night; non-existence; Numanol capsule; object; only child; order; orderly; ordnance; organ; Organian Peace Treaty; "out of your mind"; outpost; paranoid mania; patience; patriotism; pattern buffer; pawn; peace; person; persuasion; phantom; phaser; phaser torch; plan; planet; ; power system; prisoner; projectile; proof; propaganda; psychology; radiation; radiation level; raid; range; Reactor #3; red alert; remotes; report; research outpost; ; result; revenge; ruins; rules of war; sabotage; savage; scan; science officer; scream; search; second; sector; Security; sensor; sensor scan; sensor sweep; "ship out"; shock; slave labor; solid object; space; speed; starboard; Starfleet; Starfleet Command; star system; ; stuffed; subspace frequency; suffering; suffocation; surrender; surveillance; survivor; suspended in transit; sword; target area; term; terrain; thing; threat; throat; "tiger by the tail" (tiger, tail); threat; time factor; torture; "to the letter"; tracking; transmutation; transfer; transporter; transportee; transporter pad; transporter room; trap; trauma; treachery; trick; truce; truth; torture; toy; unconscious; ; victim; victory; vigilance; violence; vital organs; voice; volunteering; Vulcan; Vulcan neck pinch; wall; war; warp 9; warrior; weapon; "what the blazes"; wide field; wife; wound

External links 
 
 
 
 

de:Das Gleichgewicht der Kräfte
es:Day of the Dove
fr:Day of the Dove (épisode)
ja:宇宙の怪！怒りを喰う！？（エピソード）
nl:Day of the Dove
pl:Day of the Dove
TOS episodes