Complex sentence: Since Vietnamese were not allowed to convert and frequently lost savings by holding old worthless MPC, they would be very angry about their MPC loss and "arrange" to have the nearest U.S. base rocketed or mortared the next night.
Split into simpler sentences: Since Vietnamese were not allowed to convert and frequently lost savings by holding old worthless MPC. Angry over their MPC loss, in retaliation, the nearest U.S. base was often rocketed or mortared the next night.