In 2374 they negotiated a trading agreement with the USS Voyager for medical supplies in exchange for dilithium. However before the agreement could come into force, Voyager was boarded by a group of Kyrians. Their leader, Tedran, was killed by the Vaskan ambassador and, after further Kyrian attacks, Voyager swiftly departed.
The Vaskan/Kyrian war that erupted over the incident was devastating to the Kyrian people and resulted in an almost total victory for the Vaskans.
By the 31st century the two races lived side-by-side but the Kyrians were regarded as second-class citizens. Kyrian history included references to what was known as "The Voyager Encounter". After seven centuries, the Kyrian view of the event was hugely distorted. They believed that Voyager was a Martian warship that had been hired by the Vaskans to attack Kyrian space and that the Vaskans gave them the location of a wormhole in exchange. In their version of events, Voyager used biogenic weapons to cause mass deaths on the Kyrian homeworld and killed Tedran, who was by then regarded as Kyrian martyr.
This version of events was put forward by Quarren in his Kyrian Museum of Heritage until he discovered a back-up copy of the The Doctor in an EMH backup module found beneath a Kyrian city. This device had originally been stolen by the Kyrians in their attack and The Doctor had lain dormant in it ever since.
After he was reactivated, The Doctor was considered a war criminal. However, he explained the real history of the Kyrian/Vaskan conflict. Although this caused the old tensions between the two races to once again boil over, it led to a new understanding between them and eventually created a harmonious society. (VOY: "Living Witness")