Hello There! If you are Medal of Honor FAN and want to play multiplayer coop campaign mission with your friends
Folow this steps:

1. Download MOH GOG WARCHEST version - https://steamunlocked.org/medal-of-honor-allied-assault-free-download
2. Download MOH COOP MOD - https://www.moddb.com/mods/medal-of-honor-coop-hazardmodding
3. Launch MOH BREAKTROUGH and go to MULTIPLAYER COOPERATIVE ( choose a map )

Thats all. Good Luck Soldier!