rimary target for the attack, as was its vital port of Dinghai. When the British fleet arrived off of Zhoushan, Elliot demanded the city surrender. The commander of the Chinese garrison refused the command, stating that he could not surrender and questioning what reason the British had for harassing Dinghai, as they had been driven out of Canton. Fighting began, a fleet of 12 small junks were destroyed by the Royal navy, and British marines captured the hills to the south of the Dinghai.
The British captured the city itself after an intense naval bombardment on 5 July forced the surviving Chinese defenders to withdraw. The British occupied Dinghai harbor and prepared to use it as a staging point for operations in China. In the fall of 1840 disease broke out in the Dinghai garrison, forcing the British to evacuate soldiers to Manila and Calcutta. By the beginning of 1841 only 1900 of the 3300 men who had originally occupied Dinghai were left, with many of those remaining incapable of fighting. An estimated 500 British soldiers died from disease, with the Cameron and Bengali volunteers suffering the most deaths, while the Royal Marines were relatively unscathed.
Having captured Dinghai, the British expedition divided its forces, sending one fleet south to the Pearl River while sending a second fleet north to the Yellow Sea. The northern fleet sailed to Peiho, where Elliot personally presented Palmerston's letter to the Emperor to Qing authorities from the capital. Qishan (ᡴᡳᡧᠠᠨ), a high-ranking Manchu official, was selected by the Imperial Court to replace Lin as the Viceroy of Liangguang after the latter was discharged for his failure to resolve the opium situation. Negotiations began between the two sides, with Qishan serving as the primary negotiator for the Qing and Elliot serving as the representative for the British Crown. After a week of negotiations, Qishan and Elliot agreed to relocate to the Pearl River for further negotiations. In return for the courtesy of the British to withdraw from the Yellow Sea, Qishan promised to requisition imperial funds as restitution for British merchants who had suffered damages. The war, however, was not concluded and both sides continued to engage each other. In the late spring of 1841 reinforcements arrived from India in preparation for an offensive against Canton. A flotilla of transports brought 600 men of the professionally trained 37th Madras Native Infantry to Dinghai, where their arrival boosted British morale. Accompanying the fleet as far as Macau was the newly constructed iron steamer HMS Nemesis, a weapon to which the Chinese navy had no effective counter. On 19 August three British warships and 380 marines drove the Chinese from the land bridge (known as "The Barrier") separating Macau from the Chinese mainland. The defeat of the Qing soldiers coupled with the arrival of the Nemesis in Macau's harbor resulted in a wave of pro-British support in the city, and several Qing officials were driven out or killed. Portugal remained neutral in the conflict, but after the battle was willing to allow British ships to dock in Macau, a decision that granted the British a functioning port in Southern China. With the strategic harbors of Dinghai and Macau secured, the British began to focus on the war on the Pearl River. Five months after the British victory at Chusan, the northern elements of the expedition sailed south to Humen, known to the British as The Bogue. Bremer judged that gaining control of the Pearl River and Canton would put the British in a strong negotiating position with the Qing authorities, as well as allow for the renewal of trade when the war ended.
While the British campaigned in the north, Qing Admiral Guan Tianpei greatly reinforced the Qing positions in Humen (Bocca Tigris), suspecting (sources state that Guan had been preparing for an eventual attack on the position since Napier's attack in 1835) that the British would attempt to force their way up the Pearl River to Canton. The Humen forts blocked transit of the river, and were garrisoned with 3000 men and 