Base Delta Zero was the grim Galactic Republic, Galactic Empire, Confederacy code name for the systematic complete destruction of all a planet's 'assets' of production, including factories, arable land, mines, fisheries, and all sentient beings and droids, through a massive orbital bombardment with powerful turbolaser batteries and torpedoes and missiles.
A single Imperator-class Star Destroyer could finish a Base Delta Zero attack within several hours, and a full fleet could accomplish the dark task in less than one hour. Upon completion, the planet is virtually wiped out; the crust is melted to a depth of several kilometers, the atmosphere is lost, the seas boil over, and all life is extinguished.
Base Delta Zero was the only military code not subject to change, to avoid any confusion when it was issued. It is unknown how long this code name has been in existence, but the Galactic Republic utilized the code name during the Clone Wars, and the Confederacy executed a Base Delta Zero attack on the planet Humbarine.
The Galactic Empire carried over Base Delta Zero from the Republic, and utilized it on several planets throughout the Galactic Civil War. The most recent use of the Base Delta Zero attack was in late 14 ABY, carried out by Grand Admiral Danik Kreldin on Cochran, the captial of the Griffons Alliance.