Assault on the Geass Order

is an event that happened in Code Geass: Lelouch of the Rebellion R2.

Summary
The Black Knights swarm the Geass Directorate's city, massacring all Geass users in the city, including women and children. Due to the lack of many Knightmare Frames, the people in the Geass Directorate are quickly killed with little resistance. The only actual battle is between V.V. in the Siegfried and the Black Knights. The Siegfried is eventually brought down, leaving V.V. seriously injured and barely able to make it to Charles zi Britannia to exchange his code.