Theft of the Death Star plans

During the Galactic Civil War, the Alliance to Restore the Republic mounted a successful theft of the plans to the Death Star, the Galactic Empire's deep space mobile battle station. In doing so, the Rebels scored their first major victory against the Empire. After the battle, the plans were transmitted to Princess Leia Organa of Alderaan aboard the Tantive IV. The Empire pursued the Rebels to Tatooine, where they waged a battle to recover the plans. Organa was captured, but the Death Star plans made their way into the hands of the Rebellion. This led to the Battle of Yavin in which the Rebels found a weakness in the Death Star and destroyed the station.

Prelude
Before the start of the Clone Wars, the Sith and the Confederacy of Independent Systems began work on an ultimate weapon that would later be called the Death Star. This weapon was a deep space mobile battle station capable of destroying entire planets, and was similar to powerful superweapons built during ancient wars between the Sith and the Jedi Order. Though the Separatists worked to begin construction on the weapon, it was ultimately intended for the Galactic Empire once it replaced the Galactic Republic at the end of the Clone Wars. The weapon was completed in the years after the rise of the Empire, and became operational during the Galactic Civil War between the Empire and the Alliance to Restore the Republic.

The battle
Having recognized the destructive threat of the Death Star, the Rebel Alliance sent starships from a hidden base and stole the plans to the Death Star from the Empire. The battle to steal the Death Star plans was the first major victory that the Rebellion achieved during the war and would prove critical to their fight to restore the Old Republic. Once the Rebels secured the plans, they were transmitted to the Tantive IV, a CR90 corvette, and the plans became the responsibility of Princess Leia Organa, an Imperial Senator and leader in the Rebel Alliance.

Aftermath
With the Death Star plans in the hands of the Rebellion, the Tantive IV was pursued by the Star Destroyer Devastator, and the operation was commanded by Darth Vader, a Dark Lord of the Sith and the apprentice to the Emperor, Darth Sidious. The Devastator followed the Tantive IV to the desert world of Tatooine, where Vader captured the princess and brought her to the Death Star. Imperial forces, meanwhile, searched for two droids, R2-D2 and C-3PO, the former of whom held the Death Star plans. The droids came into the possession of Luke Skywalker who, along with Jedi Master Obi-Wan Kenobi and the smuggling partners Han Solo and Chewbacca, made their way to the Death Star and rescued Organa. Although Kenobi was killed by Vader, his former apprentice, during the escape, the princess and the others traveled to the Rebel base on Yavin 4 and participated in the Battle of Yavin. The battle was conceived after the Rebels analyzed the Death Star plans and discovered a weakness, a weakness that Skywalker exploited when he destroyed the Death Star during the battle.

Behind the scenes
"It is a period of civil war. Rebel spaceships, striking from a hidden base, have won their first victory against the evil Galactic Empire. During the battle, Rebel spies managed to steal secret plans to the Empire's ultimate weapon, the DEATH STAR, an armored space station with enough power to destroy an entire planet."

- Excerpt of the Star Wars: Episode IV A New Hope opening crawl

The theft of the Death Star plans was first described in the opening crawl of Star Wars: Episode IV A New Hope. The event has yet to be depicted in official Star Wars canon, though it will be the central plot of Rogue One. In Star Wars Legends, which is non-canon in the official Star Wars continuity, the battle was identified as the Battle of Toprawa.

Appearances

 * Star Wars: Galactic Defense
 * Rogue One
 * Star Wars: Episode IV A New Hope
 * A New Hope Read-Along Storybook and CD