Tensions escalated in the late 1960s with a series of low-level armed clashes known as the Korean DMZ Conflict . During this time South Korea conducted covert raids on the North . On January 21 , 1968 , North Koreans commandos attacked the South Korean Blue House . On December 11 , 1969 , a South Korean airliner was hijacked
a South Korean airliner was hijacked
Korean Air Lines YS-11 hijacking
North Korea–South Korea relations