Complex sentence: Post-war Japan was economically devastated which made it an ideal environment for black marketing J Force's policing duties included monitoring black market groups and also large gatherings of people on public occasions and generally keeping order until civilian government could be re-established.
Split into simpler sentences: Post-war Japan was economically devastated which made it an ideal environment for black marketeering. As such, J Force's policing duties included monitoring black market groups and also large gatherings of people on public occasions and generally keeping order until civilian government could be re-established.