On reference stardate 1/98 (c. the year 2256), as the Klingons retreated before the advancing Starfleet forces, they launched a vicious scorched earth policy on the Orion worlds they'd once occupied, in what became known as the Year of Horror, with massacres and destruction across the board. However, the Klingons left the core Orion worlds of the Rigel system untouched, apparently in an attempt to make them and the Botchok Planetary Congress appear to be Klingon allies.
In response, while the Klingons prepared to withdraw, the Orion population of the Rigel system went into a frenzy. On the night of stardate 1/9804.10, there was a wave of anti-Klingon riots and mob violence, called the Night of Empty Hands. Lynch mobs dragged collaborators—actual, suspected and entirely innocent—from their beds and executed them. In that one night, there were over 12,000 Orion victims of the riots. Two unlucky Klingons were killed; the rest had covertly boarded their transports a week earlier.