Fiera Incident details, part I
Fiera Incident details, part II
The Feira incident was an infamous event in Klingon military history.
On stardate 4326.3, the patrol forces in the Shepard sector were placed under the command of Korrd. During his command, Orion merchant raiders attacked and overran Klingon strategic material outposts. The Klingon High Command held Korrd responsible for the success of the Orions.
As a result, Korrd fell out of favor with the High Command, though an analysis by Starfleet Intelligence came to the conclusion that the charges lacked merit. General Korrd would eventually be appointed Klingon consul to the backwater world of Nimbus III.
This incident was described in Starfleet's career overview of General Korrd. (Star Trek V: The Final Frontier, okudagram)
While no definite transformation is possible, stardate 4326.3 should fall within the 2260s, i.e., some 20 years before the events of Star Trek V.