The Skirmish at Theta Ursae Majoris System was an engagement in the Theta Ursae Majoris System during the Insurrection. It was fought by the Bellicose, a captured UNSC frigate fighting on the Insurrectionist side, and the first UNSC ship armed with a Magnetic Accelerator Cannon, the UNSC Gorgon. The Gorgon was commanded by Captain Preston Cole, an officer whom the UNSC Navy was actively promoting as a hero. The Bellicose was commanded by Lyrenne Castilla, whose civilian identity was as yet unknown to the UNSC.