The massacre of the Dizonites took place by 5 BBY on the Outer Rim Territories moon Dizon Fray. It came as result of the native sentient Dizonites pushing back at the Galactic Empire's plans to establish a refueling center there.
During the early years of the Galactic Empire's rule, Project Stardust of the Imperial Department of Military Research established many outposts and facilities aimed at facilitating the construction of the Death Star. At some point, the IDMR discovered the moon of Dizon Fray in the Dizon system, a location that was ideal for the construction of a transport hub between the Imperial borderlands and the Death Star's construction site. Furthermore, the Imperial scouts who undertook geological surveys on the moon's ocean floors discovered vast deposits of raw materials that could be synthesized into fuel in the seabed and shorelines. This led to the decision to construct a refueling station on the moon, which due to its natural resources would be almost self-sustaining.
The native inhabitants of the moon, a sentient species called Dizonites, were angered by the Empire's intervention and began actively sabotaging their construction efforts. Besides their unwillingness to be conquered, New Republic historian Beaumont Kin theorized that the Dizonites had been offended by the Empire demolishing certain structures related to their religion, an event that was vaguely referenced within Imperial records.
In any case, by 6 BBY the commanders in charge of Dizon Fray were given permission to exterminate the species, which they did by dropping modified Arc Pulse Generators from Gozanti-class cruisers into the moon's oceans and activating them. The salted water of Dizon Fray's oceans was extremely conductive and the electrical charge was carried by its currents, slowly electrocuting the majority of the Dizonite population to death over the course of several hours. As they passed, they "sang" in agony, and their cries were recorded by Imperial forces as proof of their mission's completion. Its effect was, however, devastating and left many Imperials catatonic.
The recordings of the Dizonites' cries were researched by Imperial Security Bureau interrogation specialists including Doctor Gorst for their use in enhanced interrogations. Gorst and his colleagues isolated the cries of the Dizonite young as it was found they had a more devastating effect to listeners and modified the recordings, using them successfully to extract confessions from Imperial prisoners.
The massacre of the Dizonites was studied and referenced by historian Beaumont Kin in his book The Rise and Fall of the Galactic Empire as an example of an Imperial genocide as well as "the planned and casual nature of Imperial brutality against their enemies".
- Star Wars: The Rise and Fall of the Galactic Empire