In 1863 Cooper took ship to rejoin his brother, who was now at Shanghai. He became involved with the Shanghai volunteers of the Taiping Rebellion. When it ended, the opening up of China to foreign commerce proceeded. In 1868 Cooper, at the invitation of the Shanghai chamber of commerce, tried to travel through Tibet to India. On 4 January he left Hankou and travelled by way of Chengdu, Kangding, and Litang to Batang. From this point he had hoped to reach Rima on the Lohit River, over the Hengduan Mountains watershed, in eight days.