Federation-Klingon War (alternate timeline)

In an alternate timeline, the Second Federation-Klingon War was a major conflict between the Klingon Empire and the United Federation of Planets. It took place in the mid-24th century, following the deterioration of relations between the two powers. The timeline had been created when the USS Enterprise (NCC-1701-C) essentially disappeared into a temporal rift in 2344, while defending a Klingon outpost on Narendra III from a Romulan attack. (See: Battle of Narendra III)

By 2366, the war was going badly for the Federation. Forty billion lives had already been lost and Starfleet Command believed that surrender was inevitable within six months. Although the Federation had emerged victorious in several battles, including one at Archer IV, Starfleet had lost over half the fleet, and all vessels were being pressed into service, regardless of age.

In 2366, the USS Enterprise-D, a warship, encountered a radiation anomaly near Starbase 105, the same anomaly which the Enterprise-C had entered. The Enterprise-C emerged from the anomaly, and Enterprise-D commanding officer Captain Jean-Luc Picard – along with his personal confidante, the El-Aurian Guinan, who had somehow been able to "sense" the change in timeline – determined that the Enterprise-C's defense of the outpost was the pivotal point that most certainly would have prevented the war. Picard convinced Captain Rachel Garrett to take the vessel back through the rift in order to restore the intended timeline, in spite of the near-certain prospect of the ship's immediate destruction.

The war and the timeline containing it ceased to exist, following the return of the Enterprise-C to its own time. Only Guinan remembered what had happened during the change in the timeline. One other remnant of the timeline survived: the alternate Tasha Yar, who had served as tactical officer of the alternate Enterprise-D and had returned with the Enterprise-C into the prime timeline. 

Federatie-Klingon Oorlog (alternatieve tijdlijn)