HoH'egh Accord

In the Doomsday War, the HoH'egh Accord was a treaty signed in 2264 between the United Federation of Planets and the Klingon Empire, uniting them in a self-preservation pact against the army of Doomsday Machines. As a result, Commander Kargh became the first Klingon in Starfleet. (Star Trek: Phase II)