Federation-Klingon Cold War

First Contact
In April 2151, humans had their first contact with the Klingon Empire, when a ship containing Klaag, a Klingon on the run from the Suliban, crashlanded on Broken Bow, Oklahoma. Klaag was shot by a local farmer, but survived to be treated by Dr. Phlox working for Starfleet Medical.

The Vulcans advised Starfleet Command to kill Klaag, but Admiral Maxwell Forrest decided that Captain Jonathan Archer and the newly launched Enterprise (NX-01) transport Klaag back to Qo'noS, in an attempt to establish relations with the Klingons.

Despite an attempt by the Suliban to capture Klaag, Enterprise manages to get Klaag back to Qo'noS, where he is able to complete his mission where the Klingon Chancellor draws blood from Klaag, which allows scientists to find data about the Suliban threat to the Empire encoded in his DNA. (ENT novelization: Broken Bow).