China
In late 1833, Elliot was appointed as Master Attendant to the staff of Lord Napier, Chief Superintendent of British Trade in China. His position was involved with British ships and crews operating between Macao and Canton. He was appointed Secretary in October 1834, Third Superintendent in January 1835, and Second Superintendent in April 1835. In 1836, the office of Chief Superintendent was abolished and its duties were transferred to the newly created Chief of the commission. Foreign Secretary Lord Palmerston appointed Elliot to this post, however Elliot continued to use the title of "Chief Superintendent" in his official correspondence. On 16 November 1839, Elliot wrote to Palmerston regarding the opium trade: "No man entertains a deeper detestation of the disgrace and sin of this forced traffic on the coast of China. I have steadily discountenanced it by all the lawful means in my power, and at the total sacrifice of my private comfort in the society in which I have lived for some years past."
In March 1839, Lin Zexu in Canton demanded European merchants surrender their opium. When they refused, he quarantined them and surrounded their factories. Captain Elliot arrived with 20,283 chests of British opium, valued at £2,000,000. Merchants, believing Elliot would safeguard it, were appalled when he surrendered it to Lin. Elliot claimed he acted for the quarantined British community. After confiscating the opium, Lin ordered all merchants involved in the trade to leave China. Elliot and the merchants complied when the situation was very tense, and Lin subsequently destroyed the opium by dumping it into Canton Bay. In order to make the obstinate merchants comply with the order, Elliot promised the merchants British government compensation when he had no authority to do so. The joke among the happy opium merchants was that Queen Victoria was now the biggest buyer of their opium. Thus the Parliament later disagreed, believing China should pay any reparations. Frustrated by the lack of compensation, William Jardine, who had left Canton before Lin's arrival, began planning to force compensation from China through warfare, aiming to sway public and government opinion in Britain.
During the First Opium War, he was on board the East India Company steamer Nemesis during most of the battles. In January 1841, he negotiated terms with Chinese Imperial Commissioner Qishan in the Convention of Chuenpi. Elliot declared via a circular, among other terms, the cession of Hong Kong Island to the United Kingdom. However, Palmerston recalled Elliot and, accusing him of disobedience and treating his instructions as "waste paper", dismissed him. Henry Pottinger was appointed to replace him as plenipotentiary in May 1841. On 29 July, HMS Phlegeton arrived in Hong Kong with dispatches informing Elliot of the news. Pottinger arrived in Macao on 10 August, and announced two days later that Elliot's arrangements with Hong Kong would remain in place. On 24 August, Elliot left Macao with his family for England. As he embarked on the Atlanta, a Portuguese fort fired a 13-gun salute.
Historian George Endacott wrote, "Elliot's policy of conciliation, leniency, and moderate war aims was unpopular all round, and aroused some resentment among the naval and military officers of the expedition." Responding to the accusation that "It has been particularly objected to me that I have cared too much for the Chinese", Elliot wrote to Foreign Secretary Lord Aberdeen on 25 June 1842:
But I submit that it has been caring more for lasting British honour and substantial British interests, to protect friendly and helpful people, and to return the confidence of the great trading population of the Southern Provinces, with which it is our chief purpose to cultivate more intimate, social and commercial relations.
