In frequent contact with the law, Cohen was to change his life after a meeting with Dr Sun Yat-sen, father of the Chinese revolution. Cohen became a member of the Chinese National League and acted as its English-language secretary in Alberta. He represented Chinese interests to all levels of government, attempting, among other things, to combat the growing anti-Asian sentiment. He was invited to China in 1922 to serve as one of Sun Yat-sen's bodyguards and because of his habit of carrying more than one handgun was nicknamed "Two Gun."

After Sun's death in 1925, Cohen was granted a pension and the rank of general. He remained close to Chinese politics for the next 2 decades, notably in Canton, where he was involved in banking and in arranging arms deals with Western countries. Interned by the Japanese in Hong Kong in 1941, he was later repatriated to Canada. Following the communist victory in 1949, Cohen, persona grata in both Beijing and Taipei, made efforts at reconciliation - all of which failed. A man of great humanity and charm, Cohen in life came very close to matching the legends that flourished around him.