Klingon history

Like its people, the history of the Klingon Empire is violent but colorful.

Birth of the Klingon Empire
In ancient times, notably during the early part of the Zanxthkolt Dynasty, Klingons practiced mummification. 

In the 9th century AD, Qo'noS was ruled by Molor, a tyrannical ruler who was generally unpopular among the people. Kahless the Unforgettable emerged as a champion of the people, and slew Molor in single combat using the first bat'leth, the Sword of Kahless, in the Battle of Qam-Chee. Here, Kahless and the Lady Lukara fought a pitched battle in the city's Great Hall against the soldiers of Molor. While the rest of the city's garrison fled before the 500 soldiers, Kahless and Lukara stood their ground and defeated the forces. Shortly after their victory, the two began what would become known as the greatest romance in Klingon history. Kahless ruled together with his new wife as Emperor of Qo'noS, building his new empire and conquering the Fek'Ihri, despite the fact that he was not of noble birth. Kahless proved to be not only a powerful warrior, but a wise and just ruler, establishing a code of honor that was to become the template for Klingon society for centuries to come. Moreover, the defeat of Molor continues to be celebrated in the Empire in the Kot'baval Festival. 

Sometime after Kahless united all Klingons, he left. Claiming that he was going to Sto-vo-kor, he pointed to a star and said, "Look for me there, on that point of light." The place Kahless pointed out would later be called Boreth, becoming the most sacred place for Klingons. 

Kahless was not just a warrior, but also a philosopher. During his rule, he established a strict warrior code that was adopted into Klingon culture and tradition. His words are frequently invoked by warriors about to enter battle. Among his sayings are, "A leader is judged not by the length of his reign, but by the decisions he makes."  Kahless' legends were recorded in a series of scrolls called the paq'batlh. 

The way to an interstellar empire
Among Kahless' most decisive legacies is not just the creation of the Klingon Empire, but also establishing the position of the Emperor, a title which would last over the following 1,100 years. Noted Emperors include Sompek, who became famous for his conquest of Tong Vey, where ten thousand of his warriors laid siege to the city. When Sompek had taken the city, he ordered the entire population massacred and the city burned to the ground. Emperor Mur'Eq, on the other hand, became known for introducing the use of blunted bat'leths for practice, in order to make sure "his warriors kill their enemies and not each other". 

In the 14th century the Klingons suffered a devastating conquest and sack by the Hur'q. The Hur'q were a powerful race from the Gamma Quadrant, possibly using the Bajoran wormhole to reach Qo'noS. Although they did not stay long, either because of their nomadic way of life or because of fierce resistance from the Klingons, they did not leave before taking many valuable cultural treasures, including the revered Sword of Kahless. 

Also during the 14th century, some social-religious changes took place within Klingon society, which would later be described as "Klingon warriors, who set out and slew all of their gods, because they were more trouble than they were worth." 

In the beginning of the 16th century, the Second Dynasty ruled over the Klingon Empire, but was ended with General K'Trelan assassinating Emperor Reclaw then later putting to death all the members of the Imperial Family. During the next ten years, the Empire was ruled by a council elected by the people, which is referred to as "The Dark Time" by Klingon historians. Following this unique but brief period of democracy, a new group of Klingons, called the Third Dynasty, was given the titles and names of the original Imperial Family, in order to create the illusion of an unbroken line, since the true Imperial bloodlines were cut at the end of the Second Dynasty. 

According to Quark, Klingons achieved warp drive sometime after 1947. By the year 2152, Klingon vessels would be capable of warp 6. 

In the mid-21st century the reign of the last Emperor ended after which the leadership of the Empire fell to the Chancellor of the Klingon High Council. 

During the Second Empire, Chancellor Mow'ga sent a fleet to conquer the Breen, but it was never heard from again. 

22nd century
By the 22nd century, the Klingons were a major regional power, fielding a formidable military, referred to as the Klingon Defense Force. 

In 2133, a Klingon starship attempted to enter the Delphic Expanse. When it reemerged, the entire crew was anatomically inverted but still alive. After this incident, the Klingon High Council forbade all ships from entering the Expanse. 

In the late 2140s and early 2150s, the Klingons were engaged in a fierce internal struggle that, while not amounting to actual civil war, threatened to become a more intense conflict. Numerous attacks had taken place throughout the empire that were blamed on various Klingon factions; it was not realized at the time that the attacks had actually been launched by the Suliban Cabal, who were taking orders from a mysterious individual who was an operative in the Temporal Cold War.

Early contact with Humans
Although the Klingons had occasional contact with the Vulcans prior to 2151, they had not met Humans until the Broken Bow incident, in which a courier named Klaang crashed on Earth while pursued by two Suliban soldiers. After dispatching his two pursuers, Klaang was shot by a local farmer named Moore. Although Vulcan ambassador Soval advised that Starfleet authorities withhold medical treatment and allow Klaang to die, Captain Jonathan Archer intervened and insisted on returning Klaang to Qo'noS aboard his ship, the.

Archer, however, did not understand the complexity or importance of Klingon tradition, and did not realize that returning Klaang to Qo'noS was a grave dishonor and insult. However, Klaang carried with him proof that the attacks were in fact launched by the Suliban, which averted a civil war. For this service, Archer and his ship were allowed to leave peacefully. That incident fostered Klingon enmity towards Humans and was widely recognized as setting the stage for decades of future war. 

In early 2153, the Empire again encountered the Enterprise when the Human ship rescued a refugee ship from Raatooras that was attempting to flee Klingon territory. Captain Archer chose to render assistance to the refugees, but failed to realize the ramifications of his actions, particularly the embarrassment he would cause the Klingons. When the Klingons demanded that the refugees be handed over for trial, Archer refused to comply. Captain Duras of the intercepted the Enterprise and attacked it, unsuccessfully. Archer was later captured and brought to trial on Narendra III, a Klingon colony, for being an "enemy of the state." In an incendiary tribunal, Archer's "interference" with Klingon affairs earned him a life sentence to Rura Penthe. Archer managed to quickly escape from the prison, due to the rescue efforts of his crew, further embarrassing the Klingons. 

The Klingons launched several further attempts to recapture Archer, including hiring bounty hunters and sending Duras himself to track the Enterprise and recapture Archer. Duras was unsuccessful in three different attacks against the Enterprise, and he was finally killed when the Enterprise destroyed his ship during the third attack, on one of the edges of the Delphic Expanse. 

Augment Crisis
The Klingon Empire nearly went to war with Earth during the Augment Crisis in May 2154, when a group of genetically-engineered Humans hijacked a Bird-of-Prey and ejected its crew into space. Planning to devastate humanity, the Augments tried to escalate the incident by annihilating the Klingon Qu'Vat colony with a biogenic weapon. Fortunately, war was averted when Enterprise destroyed the rogue Humans responsible and saved the colony. 

A short time later, the Klingons found genetic material of the Human Augments within the wreckage of the hijacked Bird-of-Prey. Fearing that Starfleet may be attempting to create genetically-superior Humans to take over the Empire, they tried to adapt this genetic engineering to improve themselves. An unanticipated side effect was that the Augment DNA caused the Klingon cranial ridges to dissolve. The test subjects did gain increased strength and intelligence, but then their neural pathways started to degrade and they died in agony. One of the subjects was suffering from the Levodian flu, which was modified by the Augment genes to become a deadly, airborne plague that spread rampantly within the Empire posing its gravest threat since the Hur'q invasion. In the first stage of this plague, a Klingon's physiology mutated to become more Human, for which the degeneration of the cranial ridges was a symptom. With the help of a Klingon scientist named Antaak, Dr. Phlox of the Enterprise was able to formulate a cure that halted the genetic effects of the virus in the first stage, retaining the changes in appearance along with some minor neural re-ordering, but with no development of stage two characteristics, such as enhanced strength, speed or endurance. This left millions of Klingons, mostly in the warrior caste, without their ridges. As these alterations were even passed on to their children, Phlox and Antaak theorized, that surgical cranial reconstruction might become quite popular for Klingons, who want to restore their outer appearance. Nevertheless, this whole incident embarrassed the Klingons even further and the Empire no doubt began to feel much more contempt for Humans, who were responsible for creating the genetic material in the first place. 

Klingon-Federation Cold War

 * See also: Federation-Klingon Cold War

By 2223, relations had degraded to a point where the Klingon Empire and the Federation were constantly on the verge of war. 

The Federation was quickly expanding, and its territory began to approach that of the Empire. Conflicts over ownership of various star systems arose, e.g. the inconclusive Battle of Donatu V in 2245. Other disputed worlds included Sherman's Planet, the Archanis sector and Organia. Both sides refrained from committing to open warfare, although numerous skirmishes were fought between the Federation Starfleet and Klingon forces during this time.

However, in 2267 negotiations between the two sides broke down and the Federation officially declared war against the Empire. The Klingons launched an immediate offensive, seizing several planets, including the strategically important Organia. Unexpectedly, the Klingon-Federation War was brought to a sudden conclusion just days after it had begun, when the Organians, a race of massively powerful noncorporeal beings, intervened and forced both sides to end hostilities. The Treaty of Organia was then imposed, establishing a neutral zone separating the two powers and instituting a procedure, to be overseen by the Organians, through which planets along the border could be claimed and settled by both sides. 

In that same year, a brief but ultimately unsuccessful thawing in relations occurred between the Federation, the Klingon Empire, and the Romulan Empire, with the founding of a jointly-managed colony on Nimbus III. Dubbed the "planet of galactic peace," the colony quickly became an embarrassing failure for all three governments, although regular meetings between representatives did take place at the colony for at least the next twenty years. 

A number of skirmishes and hostile encounters between the Klingons and the Federation occurred over the next decade, including encounters at Capella IV, Neural, Elas and Beta XII-A. In most of these confrontations, the Klingons tried to gain strategic advantage and secure mining rights for valuable minerals, such as dilithium. 



By 2268, Klingon D7-class cruisers were used by Romulans, who retrofited them with cloaking devices. By 2285, Klingons had begun using cloaking technology themselves. 

In 2271, Kor led the Klingon Empire to a memorable victory over the Romulan Star Empire in the Battle of Klach D'Kel Brakt. By 2292, Romulans were considered "blood enemies" in the Empire. 

On two occasions over the following years, Klingon vessels fell victim to Earth-bound space probes of at least partially unknown origin. In 2273, the entity V'Ger neutralized three K't'inga class cruisers whereas another mysterious probe disabled two Klingon vessels 13 years later. 

Tensions between the Klingons and the Federation again came to a head in the 2280s with the revelation of the secret Project Genesis, a scientific program developing an advanced method of quickly terraforming worlds – but a method which also had great potential for causing destruction. While the Klingon Empire was negotiating openly with the Federation, a Bird-of-Prey under the command of Commander Kruge tried to covertly obtain the secrets of the Genesis Planet. The Klingons planned to accuse the Federation of duplicity in developing Genesis as a weapon of awesome power and using the negotiations as a cover. However, when the crew of the USS Enterprise (NCC-1701), commanded by James T. Kirk, managed to capture the Bird-of-Prey, the Klingon ambassador proclaimed a vendetta against Kirk in 2286, vowing, "There shall be no peace, so long as Kirk lives!" Because of this, as well as Kirk's previous history with the Klingon Empire, some Klingons considered him a revered figure and worthy opponent. In 2287, commander Klaa took his Bird-of-Prey all the way to Qui'Tu beyond the Great Barrier at the center of the galaxy to pursue Kirk and the USS Enterprise (NCC-1701-A). However, General Korrd, who was aboard the Enterprise, stopped him from continuing his renegade personal undertaking. 

Peace with the Federation
Although negotiations had proceeded intermittently since the imposition of the Organian Peace Treaty, no major progress was made in establishing any firm relationship between the two powers. The most notable meeting, however, was a series of negotiations at the Korvat colony in 2289, where Federation mediator Curzon Dax met with Kang. No lasting agreement was reached at this meeting, but Dax did manage to gain grudging respect from the Klingons and establish a lasting rapport. 

The situation abruptly changed with the explosion of the Klingon moon Praxis in 2293. The disaster caused major problems for the Klingon economy and military, as well as a major ecological crisis on Qo'noS itself. The Chancellor of the Klingon High Council, Gorkon, took the controversial move of proposing a full peace treaty and establishing a process for dismantling the military fortifications and outposts along their mutual border – the military emplacements and warships that the Klingons could no longer afford.

However, peace would not come easily. While en route to a meeting with the Federation president on Earth, Gorkon was assassinated by Starfleet conspirators from the USS Enterprise (NCC-1701-A), who were working in cooperation with Klingon counterparts who also opposed any peace treaty between the two enemies. Gorkon's daughter, Azetbur, was appointed as the new chancellor in her father's place. Despite enormous pressure from her advisers to abandon the peace initiative, she chose to press forward and see her father's vision fulfilled. The ensuing Khitomer Conference resulted in the signing of the Khitomer Accords, a treaty which became the foundation for peace between the Federation and the Klingon Empire. 

Ongoing détente
The Klingon-Federation relationship, however, remained rocky for the next several decades, although negotiations for a new peace treaty had begun by 2344. That same year, a single courageous act by the crew of a Federation starship would finally change relations for the better, when the USS Enterprise (NCC-1701-C) responded to a distress signal from the Klingon outpost on Narendra III, which was under attack by the Romulans. Despite overwhelming odds, the Enterprise-C rushed to the rescue and was destroyed. The crew's conspicuous heroism and ultimate sacrifice, in attempting to protect potential enemies, left a lasting impression on the Klingons, paving the way to further rapprochement towards the Federation. 

In 2346, two years after its attack on Narendra III, but still at a time when it was supposed to be "an ally" of the Klingons, the Romulan Star Empire attacked the Klingon planet Khitomer and killed almost all of the 4,000 colonists. The raid was made possible by the traitor Ja'rod of the House of Duras, who supplied the Romulans with the deactivation codes of the colony's defensive shields. With the USS Intrepid it was again a Federation vessel to be the first ship responding to the distress signal. 

Around 2349, relations between the Klingon Empire and the Federation were still described as "not too cordial." The mediator Riva gained fame for negotiating several treaties between the Federation and Klingon Empire; before Riva, there was no Klingon word for "peace-maker." By 2353, the Treaty of Alliance was signed, finally establishing a firm friendship between the two former enemies – just as the Organians had predicted almost eighty years before. Sarek of Vulcan as well as his son Spock were key figures in devising and negotiating the treaty. The Klingons even joined the Federation in some fashion, some time after 2327 but before 2365. 

Borg threat
In 2366, the Federation was attacked by a Borg cube. Shortly before the ensuing Battle of Wolf 359, Starfleet requested Klingon assistance for Admiral J.P. Hanson's fleet awaiting the attacking Borg cube. Apparently, the battle began before the Federation fleet could be reinforced. After the destruction of Hanson's taskforce, Locutus of Borg stated that "the Klingons will also be assimilated." The number of Borg drones of Klingon origin encountered by the crews of the USS Enterprise (NCC-1701-E) and the USS Voyager is stark evidence that the Empire had its share of run-ins with the Borg Collective. While the number and nature of these encounters are unknown, Voyager's first officer Chakotay, during a neural link with the Borg Cooperative, became aware of at least one pitched battle the Empire fought against a Borg cube of the same type that engaged Starfleet in the Battle of Wolf 359. The Klingon Defense Force fared little better than its Federation counterpart in the unspecified battle. 

Civil war

 * Main article: Klingon Civil War

Despite the establishment of a full peace treaty with the Federation, the Empire would not remain at peace for very long. During the reign of K'mpec, the longest-lived chancellor in Klingon history, two rival factions developed in the Klingon High Council. One, led by Duras, who was also secretly allied with Romulan interests who were seeking to split the Federation-Klingon alliance, advocated setting an independent and aggressive policy. In 2366, K'mpec, with the help of Worf, son of Mogh, even had to conceal the treason commited on Khitomer 20 years earlier by Duras' father, Ja'rod - simply to avert civil war. The other faction was led by Gowron and favored continuing the peaceful relationship with the Federation. After K'mpec died of poisoning in 2367, the two factions were on the verge of starting a new civil war. 

Although Duras was killed by Worf and his relationship with the Romulans exposed, Duras' sisters, Lursa and B'Etor, continued the struggle in their brother's place. They presented Toral, the illegitimate son of Duras, to challenge Gowron for leadership of the Council. Because the majority of the Council had been corrupted by the House of Duras, they sided with the Duras sisters and walked out of the Council when Arbiter of Succession Jean-Luc Picard rejected Toral's claim, making official the division of the Empire. 

The civil war, when it finally broke out, was as bold and bloody as any other conflict in Klingon history. The warriors of the Empire threw themselves into the fight with typical zeal – for example, Kurn was heard to shout, "Our time for glory is here!" In the first three engagements, the forces allied with the Duras family decisively defeated Gowron's allies. However, it was not generally realized at the time that the Duras forces were secretly receiving material aid from the Romulan Star Empire. The Romulans hoped that a victorious Duras family would end the Federation-Klingon alliance, creating a new Romulan-Klingon alliance to shift the balance of power in the quadrant.

However, interests in Starfleet recognized the probability that the Romulans were interfering in the conflict. Jean-Luc Picard and the USS Enterprise (NCC-1701-D) led a fleet of starships to the Romulan-Klingon border, establishing a blockade and preventing the Romulans from sending the Duras forces further assistance. When the Romulan connection was finally revealed, support quickly fell away from the Duras family, and Gowron successfully reunited the Empire under his leadership. 

The "Return" of the Emperor
By 2369, the clerics of Boreth acquired the necessary technology to "recreate" a clone of Kahless the Unforgettable using DNA from the Knife of Kirom and imprinting Kahless' memories, as written down in the sacred texts (most likely the paq'batlh), in the clone's synaptic pathways. The clerics' plan was to counter the corruption and dishonor in the Empire, by restoring a strong leadership and reinstating the position of Emperor of the Klingon Empire. "Kahless'" ascension to this post should follow his faked return from Sto-vo-kor; however, worrying about his chancellorship, Gowron was able to expose the plan of the clerics. Lieutenant Worf thereby suggested that the clone of Kahless be made Emperor, but only in the sense of a moral leader for the Klingon people with Gowron remaining chancellor of the Klingon High Council. 

Renewed hostilities with Cardassia and the Federation

 * See also: Dominion cold war, Klingon-Cardassian War and Federation-Klingon War (2372-73)

The Federation-Klingon alliance would be sorely tested in the 2370s, after the Federation made First Contact with the Dominion in the Gamma Quadrant. The leaders of the Dominion, the Founders, had the express goal of conquering all of the powers of the Alpha Quadrant, in order to prevent them from threatening the Great Link. In late 2371, the Dominion captured General Martok, a trusted adviser to Gowron, replacing him with a Changeling impersonator. 

The Changeling posing as Martok convinced Gowron that the recent civilian uprising in the Cardassian Union had been engineered and supported by the Dominion, and that the uprising heralded an imminent invasion by the Dominion into the Alpha Quadrant. To prevent this invasion from occurring, Gowron launched a massive assault against the Cardassian Empire in early 2372. Emperor Kahless condemned the invasion, but was eventually overruled by Gowron, whose goal was to conquer all Cardassian territories to ensure that it could not be taken by the Dominion.

When the Federation Council protested Gowron's actions, Gowron took it as a betrayal of the alliance and withdrew from the Khitomer Accords, ending the Federation-Klingon alliance. Although no declaration of official hostilities was made, a state of near-war developed between the two powers. The Klingons even launched a preemptive attack against the Federation outpost Deep Space 9, in order to capture the remaining free members of the Cardassian Detapa Council. However, Deep Space 9 Captain Benjamin Sisko pointed out to Gowron that a war between the Federation, the Klingons and the Cardassians was exactly what the Dominion wanted – a divided Alpha Quadrant that would be ripe for conquest in the future. Faced with this reasoning, Gowron called an end to the invasion and halted the attack against DS9. 

However, peace would not return. The Federation had refused to fight alongside their allies and had actually sided against them in battle and the Klingons could not forgive or forget this transgression easily. A tense stand-off developed over the next year, with the Klingons attempting to make political inroads against both the Cardassians and the Federation to justify their offensives. 

Finally, in late 2372 and at the Martok Changeling's suggestion, Gowron demanded that the Federation relinquish claims to a number of territories along their mutual border, namely the Archanis sector or face war. When the Federation Council refused the demands, the Empire launched an invasion with battles fought for Archanis IV, Ajilon Prime and Ganalda IV. The Federation-Klingon War was brutal, but short – only a few weeks after it began, Gowron called an end to the conflict after a Starfleet covert ops team revealed that Martok was actually a shapeshifter and the entire war had been engineered to divide the two former allies. However, some hostilities continued after Gowron's ceasefire and were only ended when the Dominion began its invasion of the Alpha Quadrant. 

The Dominion War

 * Main article: Dominion War

When the Dominion annexed the Cardassian Union in mid-2373, the Klingons were quickly defeated by the Jem'Hadar and driven from all of their Cardassian conquests. Faced with the prospect of a larger war against a much more powerful enemy, Gowron agreed to re-sign the Khitomer Accords and renew the alliance with the Federation. In addition, a detachment of Klingon soldiers was assigned to Deep Space 9, commanded by the real Martok, who had been rescued from a Dominion internment camp. 

The Empire and the Federation would ultimately fight side by side in the ensuing Dominion War that broke out in late 2373. Many of the most important engagements of the war were conducted in concert, including the Second Battle of Deep Space 9, the attack on Torros III and Operation Return. 

The anti-Dominion alliance gained new, unlikely allies in mid-2374 when the Romulan Star Empire declared war against the Dominion. Although the Romulans and the Klingons both harbored deep hatred for one other, the two former enemies managed to put aside their differences, in order to successfully fight the Dominion. 

However, ultimate victory would eventually come at a very high price. When the Breen Confederacy entered the war in late 2375, the use of the previously-unknown energy dampening weapon effectively nullified the power of Starfleet and the Romulan forces, leaving the Klingons to fight on their own, outnumbered twenty-to-one. Rather than fight a holding action, Gowron ordered that Martok launch a full-scale offensive against the enemy, claiming that they had the advantage of surprise. 

Ostensibly, Gowron hoped to achieve quick victory against the Dominion and claim all of the glory for the Empire in winning the war, without the assistance of the Federation or the Romulans. But Gowron's real plan was much more subversive and political. Gowron feared the growing popularity of Martok, who had commanded the Klingon forces on the front lines and was rapidly gaining heroic status among the soldiers of the Empire. Gowron hoped to reclaim some of that popularity for himself, by personally commanding the Klingon war effort from Deep Space 9 and by discrediting Martok in sending him on numerous hopeless missions.

When no other Klingons would protest, Worf challenged Gowron to personal combat, claiming that Gowron was a coward for jeopardizing the very existence of the Empire (and indeed the safety of the entire Alpha Quadrant), in order to satisfy his need for political security. Worf killed Gowron in the fight, thus claiming the right to rule the Empire himself; however, Worf declined the position and nominated Martok instead. 

Ultimately, the Empire shared in victory with the Federation and the Romulans, after the final defeat of the Dominion at the Battle of Cardassia in late 2375. 

Section 31 estimated that the Klingons would not recover from their losses from the Dominion War until about 2385. 

Summary of key dates

 * Around 900 AD: After slaying the tyrant Molor using the first bat'leth, Kahless the Unforgettable founds the Klingon Empire, becoming its first emperor.
 * 14th century: A race from the Gamma Quadrant, which the Klingons call Hur'q, invade Qo'noS. When they leave, they steal valuable artifacts, including the Sword of Kahless. Also during that century "Klingon warriors, set out and slew all of their gods, because they were more trouble than they were worth".
 * 16th century: Emperor Reclaw and the imperial family of the Second Dynasty are killed by General K'Trelan. For ten years, the Empire enters "The Dark Time" when it is ruled by a council elected by the people, until a Third Dynasty mimicking the 2nd one is installed to rule the Empire.
 * Mid-21st century: The reign of the last Emperor ends and the lead of the Empire falls to the Chancellor of the Klingon High Council.
 * 2133: After losing the crew of a starship, the Klingon High Council forbids all its ships any attempt to enter the Delphic Expanse.
 * 2151: First contact with Earth is initiated when the assists Klaang at proving that the Suliban Cabal is trying to destabilize the Empire as part of the Temporal Cold War.
 * 2153: Jonathan Archer of the Enterprise evades Klingon authorities three times after repeatedly "interfering" with the Empire's politics.
 * 2154: Augment Crisis: Enhanced Humans try to annihilate Qu'Vat colony, but ultimately fail in their attempt to ignite a war between the Empire and United Earth. Some months later the Empire uses residue of the Human DNA to breed augmented warriors of its own, but inadvertently creates a virus threatening its very existence. The situation is quickly stabilized, but the virus causes generations of Klingons to loose their cranial ridges amongst others.
 * 2223: Relations between the Empire and the United Federation of Planets degenerate starting a tense cold war.
 * 2245: The inconclusive Battle of Donatu V is fought between the Klingon Empire and the Federation.
 * 2267: After engaging in a brief open conflict, the Klingon Empire and the Federation sign the Treaty of Organia establishing ground rules for further interaction and the resolution of territorial disputes, e.g. over Sherman's Planet. That same year, the Empire, the Federation, and the Romulan Star Empire jointly establish a colony on Nimbus III, offcially declaring it 'the planet of galactic peace'.
 * 2271: The Empire achieves a memorable victory over the Romulans at the Battle of Klach D'Kel Brakt.
 * 2285 & 2286: Fearing it to be a new devastating Federation weapon, a diplomatic incident involving James T. Kirk arises over the Empire's attempt to gain information about the Genesis Device.
 * 2289: The Federation and the Klingon Empire hold a diplomatic meeting at Korvat colony, however without producing any substantial results.
 * 2292: By this year, the Romulans are considered "blood enemies" in the Klingon Empire.
 * 2293: The explosion of the Klingon moon Praxis causes an ecological disaster, disposing Chancellor Gorkon to pursue a full peace treaty with the Federation. Despite the subsequent assassination of Gorkon, his daughter and new Chancellor, Azetbur, participates at the Khitomer Conference, which leads to the Khitomer Accords establishing a lasting peace between the two powers.
 * 2344: Despite ongoing negotiations for a new peace treaty, the Klingon-Federation relations are again tense by this year. The Empire's alliance with the Federation would eventually be cemented by the honorable act of the Federation vessel USS Enterprise (NCC-1701-C), which responds to a Klingon distress signal from Narendra III and is destroyed while trying to protect the outpost from a Romulan attack.
 * 2346: With the help of the traitor Ja'rod of the House of Duras, the Romulans commit the Khitomer Massacre, killing almost all of the 4,000 Klingon colonists on Khitomer.
 * 2366: In order to avert a civil war, Klingon Chancellor K'mpec conceals Ja'rod's treason, due to his house's influence in the High Council.
 * 2367: After K'mpec dies of poisoning, Gowron, who is opposing the House of Duras, becomes new Chancellor. His position is quickly challenged but eventually affirmed in the brief Klingon Civil War against the Romulan-influenced, but ultimately inferior, House of Duras.
 * 2369: A clone of Kahless created by clerics from Boreth assumes the re-created, but now purely representative, position of Klingon emperor, while Gowron remains the Empire's Chancellor and factual leader.
 * 2371: General Martok is covertly abducted and interned by the Dominion, while a Changeling replaces him.
 * 2372: Led by the Martok-Changeling, the Klingon Empire starts an invasion of the Cardassian Union, which is subsequently condemned by the Federation. Later that year, the Federation's and Klingon's old dispute over the Archanis sector escalates, leading to the Klingon's withdrawal from the Khitomer Accords.
 * 2373: The real Martok is freed after the Changeling impersonating him is revealed earlier this year. The Cardassian Union joins the Dominion, swiftly resolving the Klingon's conflict with the Federation and reinstating the Khitomer Accords. Later that year, the Dominion attacks and captures the Federation station Deep Space 9, beginning the Dominion War against the Empire and the Federation.
 * 2374: With the aid of Klingon ships sent at the last moment by Gowron, the Federation recaptures Deep Space 9. Later that year, the Romulan Star Empire turns the tide of the war as it joins the Empire and the Federation against the Dominion.
 * 2375: The Dominion gains the upper hand in the war again with its alliance with the Breen Confederacy which uses energy dampening weapons. Due to a technical uniqueness of Klingon vessels, the Empire holds the front on its own for some weeks being outnumbered 20:1. Fearing the growing popularity of the successful General Martok, Gowron tries to discredit him by ordering suicidal missions, but is subsequently killed by Worf. Martok becomes the new Klingon Chancellor and, with the help of the Cardassian Rebellion, the Federation Alliance manages to repel the Dominion forces, finally capturing Cardassia Prime later that year and ending the Dominion war with the Treaty of Bajor.
 * 2385: The Klingon Empire fully recovers from its losses during the Dominion War according to an estimate by Section 31.

Alternate timelines
During the 23rd century in the alternate reality, Starfleet admiral believed war with the Klingons was imminent and recruited  to design ships and weapons, including the  USS Vengeance. Khan betrayed Marcus and transwarp beaming to an uninhabited region of Qo'nos. Captain, and  tried to capture him without alerting the Klingons, but were unsuccessful. Khan came to their rescue, singlehandedly killing the Klingons before submitting to the Starfleet officers. Afterwards, Marcus warned the incident would further exacerbate tensions between the Federation and Klingon Empire. 

In an alternate timeline, the Klingons took control of Deep Space 9 after the death of the Emissary of the Prophets Benjamin Sisko in 2372 (because the Bajorans interpreted this as sign against the Federation and tried to ally with the Cardassian Union). This timeline was avoided due to the intervention of Jake Sisko in 2422. 

In Q's anti-time future, the Klingons had conquered the Romulan Star Empire by the late 24th century. 

In Daniels's alternate timeline, the Klingons (re)joined the Federation by the 26th century. 

Related topics

 * Interstellar history
 * Cardassian history
 * Dominion history
 * Federation history
 * Human history
 * Romulan history

Klingonische Geschichte Histoire klingonne クリンゴンの歴史