Spartan-III Beta company was the second of three Spartan-III companies to be recruited, trained, and put into service. Their training began at the end of 2539, after being recruited as children orphaned by the war. Beta Company, like all Spartan-III companies, were trained on the planet Onyx, which lasted for six years until they received their augmentations at the end of their training. The Spartan-III program was run by former Spartan-II Kurt-051, and Senior Chief Petty Officer Franklin Mendez. Spartan-IIIs were known for being a cheaper version of the Spartan-II program, which included wearing Semi-Powered Infiltration (SPI) armor instead of the MJOLNIR that Spartan-IIs wore.
Notable Spartans of Beta Company were Tom-B292, Lucy-B091, Kat-B320, and SPARTAN-B312. All Beta Company members, which the exception of those in Noble Team, Tom-B292, Lucy-B091, and SPARTAN-B170 were killed during Operation: TORPEDO in 2545.
These events are depicted in the novel Halo: Ghosts of Onyx.