A short war between the Federation and the Klingon Empire in 2267, which broke out when negotiations collapsed and was stopped within days by the intervention of the Organians.
The war began with the failure of talks over disputed territory. Starfleet warned its ships to expect a surprise attack, and the USS Enterprise was sent to Organia, a seemingly primitive world of strategic value on the border.
In the Original Series episode Errand of Mercy, Kirk and Spock are caught on the planet when a Klingon occupation force arrives under Commander Kor. They carry on a sabotage campaign to the dismay of the placid Organian council. As the two fleets close for battle, the Organians reveal themselves as beings of pure energy and render every weapon on both sides too hot to hold.
The war ended there, and the Organian Peace Treaty was imposed. An Organian predicts that the two powers will one day be friends.