The pesky Asians, sometimes they’re trading too much and you have to wage a trade war on them—at other times they’re trading too little and you also have to wage a war on them.
In 1871 Koreans were trading too little. So to convince them of the benefits of relations with Americans the US government did what anybody would do. It sailed five ships with 600 military men to Korea, shot up a bunch of Koreans, and then asked the Koreans “Do you want to trade now?” The Koreans surprisingly said no.
Source: The Tales of American Empire