Sun died of cancer in 1925, and Cohen went to work for a series of Southern Chinese Kuomintang leaders, from Sun's son, Sun Fo, and Sun's brother-in-law, the banker T. V. Soong, to such warlords as Li Jishen and Chen Jitang. He was also acquainted with Chiang Kai-shek, whom he knew from when Chiang was commandant of the Whampoa Military Academy, which was located outside of Canton. His dealings with Chiang, though, were minimal since Cohen was allied with southern leaders who were generally opposed to Chiang. Cohen ran security for his bosses and acquired weapons and gunboats. Eventually he earned the rank of acting general, though he never led any troops.