[3] Lee and thousands of other Korean independence activists went into exile in the Republic of China after the violent suppression by the Japanese of the March 1st Movement.

In 1919, he started studying at the Shinheung military academy (Korean: 신흥무관학교; Hanja: 新興武官學校), which was created to build an army to fight for independence.

He was also instrumental in negotiating with the US Office of Strategic Services to create the Eagle Project, a joint mission with the Provisional Government to infiltrate occupied Korea during World War II.

[4] He was opposed to Kim Ku's South-North negotiations (남북협상; 南北協商) and allied himself with Lee Syng-man to establish a unitary government in South Korea.

Following his term in office, Lee Beom-seok served as the Korean Ambassador to the Republic of China, and as Secretary of the Interior.