Second Opium War 1856-1860
The end of the First Opium War ceded the Chinese port of Hong Kong to Great Britain and provided the British Empire with trade advantages which the Chinese quickly found to be unsatisfactory. Following the treaty, both the French and the Americans negotiated trade agreements with China disadvantageous to the Chinese and prompting Britain to demand even more favorable terms than those already agreed.
The result was the eruption of a second war between the British Empire and China, called an Opium War as was the first, in part because Great Britain wanted to legalize and monopolize the Opium trade. The United States officially declared itself neutral in the war, offering to send diplomatic envoys to assist the British and Chinese attempting to negotiate a settlement of all differences.
When France actively joined the British in military action against the Chinese – hoping to prevent British monopolization of the Opium Trade by forcing Chinese concessions – The United States sent naval forces to protect American interests in the area. The Americans did not coordinate their actions with either England or France, thus retaining its claim to neutrality, but soon actively bombarded Chinese possessions.
The American attacks led the Chinese to step up negotiations with the Americans and led to a renewed commitment of neutrality, but not to the withdrawal of American ships. The Second Opium War led to extensive intertwining treaties between varying Chinese states and warlords and their common European opponents, as well as American trade and military interests.
As in earlier overseas actions undertaken by the United States, its primary interest was the defense of its own trading needs and the requirement to obtain overseas bases for the maintenance of its expanding fleets. It largely succeeded.