Yi took part in World War I as a 2nd lieutenant (Podporuchik) of Imperial Russian Army and served on Eastern Front.

Post-WWI, Yi joined the Bolsheviks and fought in the Red Army during the Russian Civil War.

However, they were barred from joining the conference due to the Imperial Japan's objections as the supreme Asian power of the time.

In 1911, after his father killed himself, he became a military officer of the Imperial Russian Army and participated in World War I.

After the outbreak of the October Revolution and signing of the Treaty of Brest-Litovsk, Yi joined the Bolsheviks and fought in the Red Army during the Russian Civil War.