SEOUL - As well as the obvious classes like bomb-making, Kim Dong-Sik's intensive spy training in North Korea included memorising hundreds of South Korean pop songs and dance moves.
Such strategies for assimilating into South Korean society were considered essential to avoid suspicion, Kim revealed in a recently-published memoir that lifts the lid on some of the workings of the North's spy agency.
Now 51, Kim was captured in the South in 1995 and spent years undergoing interrogation before renouncing communism and joining the South's intelligence authorities as an analyst.
In his memoir, he recalls being handpicked when he was 17, and entering the Kumsong political military university in Pyongyang which specialised in nurturing secret agents to run covert operations in the South.
He was among 200 students selected each year after a national search that took into account looks, family background, school grades and, above all, unquestioning loyalty to the North Korean leadership.
The elite trainees were not allowed to leave the campus or contact anyone outside its walls - including their families.
The only exceptions were New Year greetings cards they were allowed to send home, but with no return address.
Days were filled with intense training in a large range of skills from martial arts, weapons and bomb-making to wall climbing, geology, Morse code and marine navigation.