The Death Star Uprising was a relatively large prison riot, originating in Detention Block 2180 aboard the first Death Star, where Rebel Alliance captives-of-war attempted to escape by fighting their way into two hangars and stealing a Sentinel-class landing craft. Although the prisoners' escape was completely prevented, their rioting may have only been a diversion for a more important and ultimately successful objective; a section of the Death Star plans was secretly stolen during the uprising and transported into the possession of Rebels located at a covert base on Polis Massa.
During the later stages of the Death Star's construction, captured Imperial enemies from all across the galaxy were quietly sent to the top-secret space station for interrogation and imprisonment. A group of captives of the organized Rebel movement became acquainted with an unidentified Human Jedi prisoner who was also confined to Block 2180. He had devised a simple plan to escape from the Imperial battle station that could be initiated with the co-operation of the other inmates.
The Empire was most likely not alerted of the stealthy prison-break until after the rioters had raided an Imperial arsenal, arming themselves against expected stormtrooper counterattacks.
Battle aboard the Death Star.
The first stormtroopers to become aware of the riot were those in Hangar 84G who met up with the elite 501st Legion troopers—coincidentally aboard the Death Star for an exterior inspection—that assembled in the hangar and drove off the Rebels through two blast doors that they poured in through. Most prisoners could not be recaptured without a fight and so were shot down in the unanticipated bloodshed. Hangar 84G was at last secured and locked-down by the Empire after a few minutes of assault and the Rebels instead moved on toward the Fire Control Room where the superlaser was located.
Meanwhile, stormtroopers rushed across walkways toward the superlaser, blasting a Rebel who had stolen the Death Star's schematics. Unfortunately for the Empire, the bridge normally spanning a reactor tunnel, which led to Hangar 84G on one side and the Fire Control Room on the other, had been taken down earlier. The stormtroopers instead had to use the alternate (and much longer) route through the prison area. In the meantime, other Rebels had managed to arrive at Hangar 85G, just beyond the Fire Control Room, capturing it long enough to beam a separate, partial set of the schematics to a Rebel base on Polis Massa. The other sets would be stolen at Danuta and Toprawa.
A Phase Zero dark trooper fighting in the Detention Block 2180.
All the rioters in the Fire Control Room were blasted and the Imperial troopers moved onward to Hangar 85G before the Rebels could completely board and hijack a Sentinel-class landing craft as an escape shuttle. With not more than two minutes before take-off, stormtroopers burst into the hangar eliminating as many escapees as they could. Their Jedi leader at last exposed himself in a desperate sprint toward the shuttle, but a moment later, Imperial shock troopers had blown it up.
The frenzied Jedi ignited his lightsabers and cut through any trooper that stepped into his path. The Jedi and his squad of troopers were eventually gunned down. Imperial intelligence later tracked the missing schematics and the handful of Rebels who managed to escape to Polis Massa, where an even more fiery skirmish would eventually break out.
The prison break was a great embarrassment to Darth Vader's supposedly "Elite" 501st Legion, and thus an embarrassment to Vader himself. As punishment, Vader had the Legion reassigned, from their "comfortable" position on the Death Star, to his army, helping him search the galaxy for both the stolen Death Star plans and the escaped Rebel prisoners. The search would prove futile, however, as the plans were not found in time to prevent the destruction of the Death Star. Despite this, the punishment made sure that the Legion was not stationed on the Death Star when it was destroyed. The troopers that did take their place, however, were utterly doomed.