- "That 'Base Delta Zero' initiative the Empire keeps talking about? The new 'key to planetary liberation'? Don't believe it. It's a military code phrase, and it means TOTAL EXTERMINATION OF A TARGET POPULATION. It's completely loathsome."
- ―Sabine Wren, in her private journal
Base Delta Zero (Δ) was the naval code for a type of orbital bombardment capable of completely destroying the surface of a planetary target. It was used by both the Galactic Republic and its successor state, the Galactic Empire, although the former only used it as a last resort against enemies entrenched deep underground, while the latter deliberately used it as a tool of planetary-scale extermination.
Base Delta Zero (Δ) was an extreme form of orbital bombardment capable of melting a planet's upper crust to molten slag, which in practice could amount to completely destroying said planet's population.
The Base Delta Zero initiative was originally introduced by the Galactic Republic, as a last resort against enemy armies entrenched deep underground. After the Republic was replaced by the Galactic Empire at the end of the devastating Clone Wars, the code remained in use. However, the Empire publicly claimed that Base Delta Zero was only involved in planetary liberations, while in actuality the tactic was used for mass exterminations. In her journal, the Mandalorian artist and freedom fighter Sabine Wren wrote about how the Empire had lied about the true meaning of the code.
On one occasion on Lothal, Wren managed to access the data contained within the AJ^6 cyborg construct worn by Tseebo, an employee of the Imperial Information Office. There, she saw information about a five-year plan for the Empire's development in the Outer Rim Territories. When she reached a screen featuring the characters Δ, Wren was barred further access.
Within the Empire, Base Delta Zero was also part of everyday slang. When Zare Leonis, cadet at the Academy for Young Imperials, began fighting with Nazhros Oleg after being provoked, Lieutenant Currahee warned their unit, Aurek, that she would be "going Base Delta Zero" on them if there were any further screw-ups.
- Star Wars Rebels – "Rise of the Old Masters" (First mentioned)
- Star Wars Rebels – "Empire Day" (Mentioned in hologram only)
- Servants of the Empire: Imperial Justice (Mentioned only)