After about three years of rigorous training, during which seven of them died, Unit 684 set off in rubber inflatable boats towards North Korea on their mission. However, en route, it was terminated, and the members forcibly turned back by their instructors. This was because the Korean governments were now looking towards a peaceful reunification.
In August 1971, the KCIA cancelled the mission for good, ordering the instructors to terminate all Unit 684 trainees, and erase all evidence of the project. Before they could be murdered, the Unit 684 members rose up to kill their overseers.
They then attempted to make their way to the Blue House (South Korean President’s House) in a rebellion. Most of them, however, committed suicide with hand grenades when roadblocked, and confronted by government troops, before they could cross the Han River. The survivors were sentenced to death by a military tribunal."