The Battle of Tong Vey was a legendary Klingon battle in which Emperor Sompek lead an army of ten thousand warriors against the city of Tong Vey. The army laid siege to the city for a long time before the city fell. Soon after, the warriors burned the city to the ground, and killed all survivors, soilders or otherwise.
Worf had a holoprogram of the battle aboard the USS Enterprise-D. He brought it to Deep Space 9, where he often used it in Quark's holosuites. He used the program a day before he commanded the USS Defiant in a convoy mission in the Pentath system. His fondness of the program came back to haunt him when Ch'Pok used the holoprogram which only had one ending, that of the massacre, as an example of letting bloodlust get the better of him. (DS9: "Rules of Engagement")
The computer game Star Trek: The Next Generation - Klingon Honor Guard depicts a very different version of the Battle of Tong Vey. In a holodeck recreation, Sompek infiltrated the city himself after his armies failed to defeat it. He destroyed the cooling system of the city's geothermal power plant, causing the city to burn to the ground.