Sometimes good relationships get off to a bad start. The United States and South Korea are a case in point. Today, Seoul is a valued American ally. Just last month, South Korean president Park Geun-hye became the sixth Korean president to address a joint session of Congress. President Obama said that President Park’s decision to make the United States her first overseas visit as president “reflects the deep friendship between our peoples and the great alliance between our nations.” But U.S.-Korean relations started with conflict rather than cooperation when on June 10, 1871, the U.S. Navy expedition sent to open relations with Korea instead waged the Battle of Ganghwa (or Shinmiyangyo).

The backdrop for the hostilities was the American desire to establish trade relations with Korea. Like its neighbor Japan, Korea in the mid-nineteenth century was hostile to foreign influences, so much so that it earned the nickname of “the Hermit Kingdom.” Japan agreed to sign a commercial treaty with the United States only at the point of a gun after a fleet headed by Commodore Matthew Perry appeared in Tokyo Bay in 1854. American merchants hoped that a similar treaty could be struck with Korea. The outbreak of the Civil War ended U.S. interest in Asia for a time. But after Lee’s surrender at Appomattox, American merchants again turned their eyes to the region.

The “Korean Expedition” that steamed out Nagasaki, Japan in May 1871 with five U.S. warships and 1,230 men under the command of Admiral John Rogers had two goals. The first was to open Korea to American merchants. The second was to learn the fate of the U.S. merchant ship, The General Sherman. It had disappeared after sailing up the Taedong River (which leads to modern day Pyongyang) in August 1866. The ship disregarded warnings to stop, ran aground upriver when the tide receded, and then sent out raiding parties. The Koreans eventually attacked the ship and killed its crew. Americans knew none of this because the Koreans refused to say what had become of the ship. So when the Korean Expedition set sail, the New York Times assured its readers that the effort would produce a “Detailed Account of the Treacherous Attack of the Coreans on Our Launches” and deliver “Speedy and Effective Punishment of the Barbarians.”

On June 1, the American ships entered the Ganghwa Straits on the west coast of Korea. Their goal was to steam up the Han River, which led to the capital city of Hanyang (modern day Seoul). The Korean king, however, had barred foreign ships from entering the Han. So when the American ships passed by, the Korean garrison onshore fired. Their outdated weapons did no damage, but that didn’t matter to Admiral Rogers. He gave the Koreans ten days to apologize for what he regarded as an unprovoked assault.

The Koreans refused to comply. So Admiral Rogers made good on his threat. On June 10, the U.S. ships attacked the Choji Garrison on the island of Ganghwa-do. It was a mismatch from the start. The garrison was lightly defended, poorly equipped, and badly outnumbered. U.S. marines and sailors then went on to overrun several other Korean posts on the island. When the smoke cleared at the end of the day, the Americans controlled Ganghwa-do at the cost of three dead. The Koreans weren’t so fortunate. They lost more than two-hundred-and-forty men.

Koreans call the fighting on Ganghwa-do "Shinmiyangyo," which literally means “Western Disturbance in the Shinmi Year.” The American victory marked the first time that the stars and stripes were raised over Asian territory by force. Fifteen Americans—nine sailors and six marines—earned Medals of Honor for their bravery during the campaign, making them the first Medal of Honor recipients to be honored for fighting on foreign soil.

The Americans hoped that their victory would persuade the Koreans to negotiate. It didn’t. Instead, they sent reinforcements in large numbers and armed with modern weapons. Recognizing that the odds had shifted, the U.S. fleet pulled up anchor and set sail for China on July 3. The United States would not get a treaty with Korea until 1882. That agreement came about in good part because the Korean king was hoping that U.S. support could help him preserve Korea’s independence from China.

The 1882 treaty established “permanent relations of amity and friendship” between the peoples of Korea and the United States. That amity with South Korea continues to this day. But most Americans don’t know that, as the historian Robert Kagan put it, “the self-proclaimed disinterested and peace-loving Americans had introduced themselves to Korea by killing its people.”