Battle of HarOs

The Battle of HarOs was a military conflict fought by the Klingon Empire sometime prior to the mid 24th century. Data created an abstract expressionist painting of the Battle of HarOs, which he presented to Worf as a gift on his thirtieth birthday. 

Years later, during his mission to taD, Worf would compare a "hideous" piece of native al'Hmatti art to Data's depiction of the Battle of HarOs.