In 2267, negotiations between the Federation and the Klingon Empire were on the
verge of breaking down. The Klingons had issued an ultimatum to the Federation to withdraw from disputed areas claimed by both the Federation and the Klingon Empire of face war. The hostilities came to a head at planet Organia, the only Class M planet in the area. Unknown to either combatant, the Organians were incredibly advanced non corporeal life forms who imposed the Organian Peace Treaty on both parties, thus effectively ending armed hostilities.
The Klingons entered into a brief alliance with the Romulan Star Empire around 2268,
when an agreement between the two powers resulted in the sharing of military technology and spacecraft designs, providing the Romulans with Klingon battle cruisers. In turn, the Klingons learned of the Romulan cloaking device.
The Klingons Can Be Seen In The Episodes, "Errand Of Mercy," "Friday's Child," "The Trouble With Tribbles," "A Private Little War," "Elaan Of Troyius," "The Day Of The Dove," and "The Savage Curtain."
