In the early afternoon of Aug. 23, 1971, Seoul was in a state of emergency. A group of North Korean special forces was allegedly about to invade the city. Just past two in the afternoon, a short but intense exchange of fire took place at Yeouido, along the Han River, not far from where the National Assembly was under construction.

Soon, though, it became clear that the incident had nothing to do with North Korean commandos. Instead, mutineers from a secret South Korean military contingent known as Unit 684 had penetrated the capital before being brought to heel. Stranger still, their original mission had been to kill DPRK leader Kim Il Sung.