- "Sir, incoming. Sector delta. Long-range missiles!"
- ―A clone trooper to Jedi General Pong Krell
Sector delta was a location near the Umbaran airbase on the dark world of Umbara in the Expansion Region. During the Battle of Umbara, the Galactic Republic's 501st Legion was able to capture the Umbaran airbase from the Umbaran militia. While stationed in the base, the 212th Attack Battalion came under fire from long-range missiles supplied by a Separatist supply ship during their effort to take the Umbaran capital. Jedi General Pong Krell, secretly an agent of Dooku, strategized to deploy all of his troops to capture the capital.
When Advanced Recon Commando CT-5555 "Fives" became aware of the plan, he remarked that the battalion would not make it past the delta. Sometime later, while Clone Captain CT-7567 "Rex" conversed with General Krell in the command tower, a clone trooper noted that there were incoming missiles heading to sector delta.