While serving the Korean liberation army, he participated activities with the Office of Strategic Services (OSS; the predecessor of the CIA).

[1][2] After returning to Korea, Chang worked as a secretary of Kim Ku and participated in Lee Beom-seok's Chosun Ethnic Youth League.

From 1975, when he was preparing to fight against the Park Chung Hee administration, he died mysteriously in Pocheon, Gyeonggi Province.

The South Korean government announced that Chang's death had been caused by loss of footing while climbing down a mountain.

To such doubts, the Park administration declared the state of national emergency and arrested anyone who mentioned the death of Chang Chun-ha.