Cohen fought with the Canadian Railway Troops in Europe during World War I where part of his job involved supervising Chinese labourers. He also saw some fierce fighting at the Western Front, especially during the Third Battle of Ypres. After the war, he resettled in Canada. But the economy had declined and the days of the real estate boom were long over. Cohen looked for something new to do, and in 1922 he headed to China to help close a railway deal for Sun Yat-sen with Northern Construction and JW Stewart Ltd. After disembarking in Shanghai, Cohen went to see George Sokolsky, the New-York born journalist who worked for Sun's English-language Shanghai Gazette. Sokolsky arranged an interview for him with Eugene Chen, Sun's English language secretary. Cohen was hired, and soon ensconced himself at Sun’s home at 29 Rue Molière in the city’s French Concession. He then got right to work.