Breakthrough: With Prejudice is the fifteenth mission of Metal Slug: 1st Mission.
The Hero boards an SV-000 and travels to the main Rebel base. The first half is traversing over rails and girders. The second half is an autoscroller where missiles are shot and tanks are placed for the screen to crush the SV-000 to a wall. The last stretch is wading over a water pool with Rebel Divers underwater.
If the SV-000 is destroyed or falls to a pit, then the Hero is sent to Prison Camp. The first section is a long hallway and various doors, with the fifth door being the true exit. The second section is using a handcar to travel between fire and later jumping on blocks over spikes. The last section is riding handcars over spikes and dodging missiles and Rebels.
Completing either the main mission or Prison Camp both proceed to the final mission (Fierce Battle).