Copy battle_command.mod and the battle_command folder into:
Documents/Paradox Interactive/Hearts of Iron IV/mod/
Enable "Battle Command" in the HOI4 launcher.
In-game, while at war: Decisions -> Battle Command -> Take Command of the Battle (25 PP, 20-day cooldown).
Requires a field marshal. Plans form a rock-paper-scissors cycle; commander skill adds to your odds.
