Though it's widely overlooked today, the U.S. has had a military presence in Asia for more than 200 years. The East Indies Squadron was formally established by President Andrew Jackson in 1835 to protect American property and trade in Asia, but U.S. warships were protecting American interests in Asia before then. In fact, American merchant vessels reached China as early as the 1780s.

Ships engaged in trade in Asia were at risk from pirates, and shipwrecked sailors were at the mercy of locals. Additionally, American whaling ships came to dominate the whaling trade in the Pacific and were also vulnerable to piracy and to incidents when they docked at Pacific ports to refresh supplies. American warships investigated incidents of piracy, including occasional punitive expeditions to punish pirates or their maltreatment of shipwrecked sailors.

Given the distances involved, the captains of warships had a great deal of discretion to commit their ships to action as they saw fit. Before they left port, they were usually given deliberately broad instructions by the Secretary of the Navy or by the President. U.S. ships got to Asia by way of Cape Horn at the tip of South America, or by the Cape of Good Hope around southern Africa, as there was no Suez Canal to shorten the very long voyage until 1869, and there was no easy communication between Washington and California until the transcontinental telegraph in 1861. California became a state in 1850, and the Navy was quick to establish a naval base there, setting up the Mare Island Navy Yard base near San Francisco in 1854. The first warship constructed there was in 1859.

An American warship was involved in a punitive expedition in the Pacific as early as 1813-14 at Nuku Hiva in the Marquesas. American naval landing forces fought battles at Quallah Batoo in 1831 and at Muckee in 1839, both in Sumatra. The Navy was involved in a battle in the Gilbert Islands in 1841. The Navy sometimes cooperated with the Royal Navy in actions against pirates off the Chinese coast and was involved in fighting in China in the 1850s and 1860s. There were incidents when American warships were involved not only in China, but also Vietnam and Japan. Americans participated in the violence in Japan as the Shogunate fell and the Meiji restoration began.

Korea was facing demands to open for trade from the Russians, British, French, Americans, and Japanese. The ruler of Korea was Yi Ha-eung, better known as the Daewongun (also spelled Taewongun), the regent for a child king, his own son. The Daewongun was strongly xenophobic and acted to maintain Korea's traditional isolation from the outside world (Boot 58).

In 1868, the U.S. East Indies Squadron was renamed the Asiatic Squadron. It was based largely in Hong Kong, but was also allowed to develop facilities in Chefoo in China and at Hiroshima and Yokohama in Japan.

As it turned out, the largest military action of the U.S. Asiatic Fleet before the Spanish-American War was a mostly forgotten war with Korea in 1871, now known as the Korean Expedition.