Barracks D4 was a structure established by the Galactic Empire's military and located within Timira City on the planet of Kamino. It was in 1 BBY when Starkiller, a clone of Galen Marek, who was the deceased Sith apprentice of Sith Lord Darth Vader, fled from the city.
Unit 6 made reference to Barracks D4 as the escape unfolded. A stormtrooper indicated that the barracks had suffered considerable structural compromise because Vader compelled an elevator shaft to collapse into it.
The LucasArts video game Star Wars: The Force Unleashed II, which debuted in 2010, included the initial mention of Barracks D4. The stormtrooper's statement is subject to randomization with each playthrough, so the report of damage to Barracks D4 is not guaranteed.