On 19 April 1950, he won the Boston Marathon with a record time of 2:32:39, under coach Sohn Kee-chung, the marathon winner at the 1936 Berlin Olympics.
On 19 April 1950, he achieved a remarkable success by winning the Boston Marathon with a world-class time of 2:32:39, under the guidance of coach Sohn Kee-chung, who had previously won the prestigious marathon at the 1936 Berlin Olympics.