In 1978, Jeong was appointed Army Chief of Staff, the most dominant role in the South Korean military. On the evening of 26 October 1979, while Jeong was dining at the Blue House presidential compound, South Korean President Park Chung-hee was assassinated at another facility in the compound. The assassin, Kim Jae-gyu, immediately sought out Jeong with a view to having him take over the presidency.