Here's how it works:
    - Campaign Mode: press the START button on Player 2 game pad upon entering active gameplay. Ending the game or exiting to the main menu will automatically return to full screen single player mode.
    - Raid Mode: pressing the START button on Player 2 game pad in the Vestibule (the staging area) will activate split-screen mode. Select character, configure your loadout, and select Raid missions as normal. Exiting the Vestibule and backing out to the main menu will automatically end split-screen mode.
    - Alternatively, simply disconnecting the 2P controller will force the game back into full screen single player mode.