When Europe and the USA opened up trade with China in the 18th and 19th centuries, there were all sorts of wonderful products they coveted, like furniture, silk and tea, but the Chinese had no particular desire for Western products. Britain had (literally) a quick fix for this, developing poppy fields in India and selling opium to China. Very soon there was an enormous Chinese demand for opium. The Chinese government tried to put a stop to this by banning the import of opium, to which a large proportion of the population in coastal cities became addicted. In the 1st Opium War, when the British navy shelled these cities into submission, China was forced to provide unfettered access to trade with the Treaty of Nanjing in 1842.
That would teach the Chinese to interfere with free trade!