Derra IV was a planet in the Derra system of the Mikaster sector, located in the Expansion Region. It was a minor world of little value and had been relatively overlooked by the Empire early in the Galactic Civil War. This made it an ideal site for Rebel Alliance operations.
Since before the Battle of Yavin, Derra IV had been the site of an outpost and storage dump for the Rebellion.
As of 1 BBY, its Imperial governor was Dol Donar II. Donar hated the Alliance with a passion, until he found his demise that same year.
Early in 3 ABY just days before the Battle of Hoth, it was the site of a crushing ambush in which Imperial forces destroyed a vital Rebel convoy and its escorts on their way to Hoth. The ambush was led by (and credit claimed by) Darth Vader, but masterminded by Grand Admiral Thrawn.
The PC game Star Wars: Rebellion mistakenly places Derra IV in the Kanchen sector, which is actually located in the Core Worlds.