Yeo Un-hyung joined the independence movement in 1918, forming the New Korea Youth Party in Shanghai. In 1919, he sent representatives to the Paris Peace Conference to promote Joseon's independence and served as deputy foreign minister for the Shanghai Provisional Government.
In November 1919, Yeo Un-hyeong was invited by the Japanese cabinet. In a speech to hundreds of Japanese journalists, he insists on the independence of Joseon and criticizes the Japanese government. The Japanese cabinet, which tried to appease Yeo Un-hyeong, is facing a backlash and is facing the dissolution of the House of Representatives. In 1929, Yeo Un-hyung was arrested by Japanese police and jailed for three years. After being released from prison, he became the president of the Chosun Ilbo and posted a photo of Sohn Ki-jung deleting the Japanese flag when he won the marathon at the Berlin Olympics.
In August 1944, Yeo Un-hyeong gathered patriotic forces from left to right to form a national foundation alliance. This will be the foundation of the National Foundation Preparation Committee, which has a system two days after its liberation. However, the path to establishing a unified government was not easy. The left-right confrontation has become intense within the trusteeship of the Moscow Tripartite Conference. The first joint committee of the U.S. and Japan, which was trying to discuss the formation of a unified provisional government, collapsed.
In June 1946, Rhee Syng-man proposed the establishment of a single government in Jeongeup, and Yeo Un-hyeong opposed it. Yeo Un-hyung, who pushed for a left-right joint effort to establish a unified government, is bombarded with criticism and attacks from both camps, and constant terror attacks occur against him. Eventually, Yeo Un-hyung was assassinated on July 19, 1947. His death stops his dream of establishing a unified government.