[3][4] He came from a family of missionaries and academics going back several generations; for example, his ancestor Mason Locke Weems was a minister and noted biographer of George Washington.
[3][4] The family arrived and lived in Korea during a tumultuous time, shortly after the Japan–Korea Treaty of 1910, in which the Empire of Japan forcefully colonized the country.
He built over 32 churches, trained 25 Korean preachers, enrolled hundreds of children in schools, and served as a member of the board for Yonsei University.
[5] On December 7, 1941, Japan attacked Pearl Harbor, which led to the entry of the United States into World War II.
In February 1942, the Military Intelligence Service (MIS) hired Weems and made him its main analyst on Korean issues.
[7] On February 27, 1943, he gave a presentation at the invitation of the California Korean Reserve at the Palace Hotel, San Francisco, entitled "Korea Yesterday and Tomorrow".
He then moved to the OSS office in Anhui between June and August 1945, and was placed in charge of a training camp for Koreans guerillas.