The Crossbone Vanguard is a private military force founded and backed by the Ronah family and the main antagonists of Mobile Suit Gundam F91. They seek to conquer the new Frontier colonies at Side 4 so they can use them to establish an aristocracy called Cosmo Babylonia.
With backing from Meitzer Ronah, the Crossbone Vanguard was formed in U.C. 0106, with its leader being Meitzer's son-in-law, Carozzo Ronah, referred to as "Iron Mask" due to his Cyber-Newtype mask.
In U.C. 0123, the Crossbone Vanguard began its invasion, attacks the Frontier IV colony and easily crushing the Earth Federation forces stationed there. The Crossbone Vanguard then then sent their forces to take control of the Frontier I colony. In the course of fight, Carozzo, piloting the XMA-01 Rafflesia, fought the F91 Gundam, piloted by Seabook Arno. Carozzo was defeated by Seabook and died in the destruction of his mobile armor.
- Meitzer Ronah - Founder
- Carozzo "Iron Mask" Ronah - Commander
- Dorel Ronah - Ensign
- Zabine Chareux - Lieutenant
Principality of Zeon