The Broken Bow Incident was an event in Human-Klingon history that took place in Broken Bow, Oklahoma on Earth and established relations between Humanity and Klingons, also involving the Suliban. (ENT: "Broken Bow")
Acting on orders from a mysterious representative from the 28th century, the Cabal staged numerous assaults within the Klingon Empire, making it seem as if one Klingon House was attacking another. This was because the future-residing authority wanted to change history by disrupting the empire.
The Klingon High Council sent a Klingon courier named Klaang to Rigel X, to meet the leader of a Suliban resistance unit called Sarin. Once Klaang's scout ship stopped at Rigel X, Sarin gave him vital evidence – proof that the attacks were being staged by the future-commanded Cabal. This evidence was secretly written into Klaang's blood. Delivery of the information would prevent the Klingon Empire from being thrown into chaos.
In an effort to ensure that the proof of Suliban culpability for the recent attacks in the Klingon Empire was never delivered, two soldiers allied to the Cabal – one of whom was a friend of Silik, the cabal's leader – pursued Klaang to Earth in a ship that was equipped with a cloaking device. Klaang's ship made no stops between leaving Rigel X and arriving at Earth. (ENT: "Broken Bow")
The pair of Suliban soldiers likewise crash-landed near the town. (ENT: "Detained") Klaang was chased from the wreckage of his craft by the pair of Suliban. They targeted Klaang with pistols, without downing him, while all three ran. A plume of smoke from Klaang's crashed ship and the disturbance of the weapons fire drew the attention of a farmer named Moore, on whose land the Klingon and pair of Suliban were trespassing.
As Moore fetched a plasma rifle from his farmhouse, Klaang rushed inside a silo which was situated in a nearby clearing. Finding the door to the silo locked, one of the Suliban soldiers used one of his genetic enhancements to slide under the door. He then opened it, from the other side, for his companion. However, Klaang hurriedly exited the building from another door, near the top of the construction, before racing a few feet away from the silo and firing at it with a disruptor he had with him. This caused the silo to be destroyed in a methane explosion which incinerated the Suliban and created shock waves that hurtled Klaang to the ground.
As Klaang picked himself up, Moore raced into the clearing, then paused to observe the strewn remnants of his silo. Both of them armed, the Klingon and the farmer confronted one another. They were unable to understand each other's language, though, leading to Moore finally shooting Klaang with the rifle, sending him flying backwards again – so that his head landed at the edge of the corn – and rendering him unconscious, near death. (ENT: "Broken Bow")
Following the incident, Moore gave a statement that included him claiming that he had shot Klaang in self-defense and only vaguely describing the Suliban involved in the event. Additionally owing to the incineration of the Suliban corpses, Starfleet and the Vulcan High Command were initially unable to identify the persons who had been pursuing Klaang, who was treated at Starfleet Medical while remaining unconscious. However, Vulcan sensor logs showed that the chasers had been using stealth technology. Similarly, even though Klaang's ship had been destroyed, navigational logs were salvaged from the craft, which informed the Vulcans of Klaang's visit to Rigel X.Despite the incident having occurred on Earth, there was considerable dispute over whether it would be the Vulcans or Starfleet which would return Klaang to his homeworld of Qo'noS. Considering that the Klingons would find Klaang's extreme injuries a disgraceful condition, the Vulcans persuaded the Klingon Empire into demanding that the Vulcans expedite his return, disconnecting Klaang from life support, rather than the Klingons dispatching a fleet of warbirds to Earth. Starfleet eventually insisted that Enterprise be allowed to return the Klingon alive, however, since Captain Jonathan Archer required a mere three days to ready the newly commissioned NX-class Enterprise and its crew for departure on the journey from Earth to Qo'noS, which usually took four days. After the starship launched, Silik asked his mysterious benefactor if he could alter the timeline in order to prevent the deaths of the two Suliban, but the future inhabitant refused this request. On his instruction, the Suliban made another attempt to retrieve Klaang once he had regained consciousness, which did succeed. It was only at this juncture that Vulcan Sub-Commander T'Pol admitted to the Human crew members of Enterprise the evidence of Klaang having been on Rigel X. In an effort to recover him from the Suliban, Enterprise made a detour to Rigel X, where Archer learned more about the events preceding the Broken Bow Incident from Sarin, although she was killed by members of the Cabal shortly thereafter. Enterprise's crew eventually managed to deliver Klaang to Qo'noS, where the hidden information he had attempted to courier there was finally revealed to the Klingon High Council. (ENT: "Broken Bow")
When T'Pol advised Captain Archer that a farm on the Akaali homeworld had been chosen as a good landing site for an away team from Enterprise to visit that planet, Archer responded that the farm's qualities of being remote and sparsely populated – reducing risk of cultural contamination – must be "why aliens are always landing in cornfields," indirectly referring to the Broken Bow Incident. (ENT: "Civilization")
As a result of Silik's failure to fracture the Klingon Empire, his mysterious time-residing superior punished him by extracting one of his genetic enhancements, ensuring that enhanced vision which Silik had possessed, up until then, was surgically removed by a Suliban medic. (ENT: "Cold Front")
Some details regarding the Broken Bow Incident were uncovered by the Tandaran intelligence agency. While Captain Archer underwent temporary imprisonment in the Tandarans' Detention Complex 26 in circa 2152, Colonel Grat reminded Captain Archer of the event. Grat also questioned Archer about the incident, asking the captain to provide insight into why the Suliban had been chasing a Klingon in Broken Bow, but Archer refused to reveal specifics. (ENT: "Detained")
In the alternate reality of 2259, Admiral Alexander Marcus told James T. Kirk that since Starfleet had first learned of the existence of the Klingons, they had conquered and occupied two planets that they knew of and fired on their ships a half a dozen times. (Star Trek Into Darkness)
The disastrous first contact between Humans and Klingons led to decades of war between the two races. By 2367, Starfleet came to regard the incident as a primary reason for making the controversial decision to typically conduct surveillance before initiating contact with a species. (TNG: "First Contact")