In 3 BBY, an Imperial medical frigate was stolen by the rebellion, with the assistance of the ship's captain and a squadron of rebel starfighters. The Empire, investigating the theft, discovered that the prime minister of Christophsis, along with many other government officials, including the planet's senators, were backing the Christophsian rebels, who had been involved in the incident.
The Empire moved swiftly, arresting the prime minister, senators, and territorial supervisors. The city of Tophen, the prime minister's hometown, which the Empire had determined was the center of the planet's rebel activity, was "pacified." The prime minister was executed for treason, and the senators and territorial supervisors were sent to Imperial work camps.
Grand Moff Wilhuff Tarkin gave a speech detailing the Empire's crackdown to the entire Imperial Senate, as a warning about what would happen to other worlds that dared to defy the Empire.