When a band of terrans landed on Ursa, including terraformers, surveyors and soldiers, it became the site of a massive battle against the zerg as Jon Dyre won the campaign virtually single-handedly. Dyre believed the terrans had been secretly infested and killed his own men, which he believed to be "mercy killing". He wrote a report about this secret infestation, but it was ignored. He was hailed as a hero, and the campaign made his career.
Ursa's primary military base was a site chosen to showcase the new Viking combat system. The presentation went awry as the seemingly insane pilot, Jon Dyre, destroyed the base and attacked civilians, claiming to be battling against a form of corruption. His former student, Wes Carter, attempted to stop him, believing the colony would be lost if Dyre were left unchecked.
Carter managed to trap Dyre and demand an explanation for his actions. Dyre admitted to killing his own men and the effect that act had on him. Then he self-destructed his Viking without ejecting. The Dominion covered up the incident as best they could and set about rebuilding the damaged colony.