[citation needed] In 1931, he ran as the representative of his province at the Chōsen Shrine Competition (조선신궁대회) in Seoul (Keijō), and placed first.

[5] Sohn first competed in the 1,500 and 5,000 m, but turned to longer distances after winning the Chōsen Shrine Competition in October 1933.

[7][8] According to the International Association of Athletics Federations, the record remained unbroken until Sohn's own trainee, Suh Yun-Bok, won the 1947 Boston Marathon.

It cited his efforts to sign his Korean name and his stress on Korea's status as a separate nation during interviews.

The move was part of the Korean Olympic Committee's repeated requests to acknowledge Sohn's background.

[11] Sohn refused to acknowledge the Japanese anthem while it was played at his award ceremony and later told reporters that he was ashamed to run for Japan.

[3] When the Dong-a Ilbo published a photograph of Sohn at the medal ceremony, it altered the image to remove the Japanese flag from his running tunic.

The Kempetai military police imprisoned eight people connected with the newspaper and suspended its publication for nine months.

[12][13] For winning the marathon, Sohn was to have received an ancient Corinthian helmet from the 8th century BC, which was discovered at Olympia, Greece, and later purchased by a newspaper in Athens to give as an Olympic award.

[18] Sohn was the team manager for the Korea at the 1948 and 1952 Summer Olympics and was the nation's flag bearer in the London 1948 opening ceremony.