Excerpts from Books and Wikipedia
"When in 1839, China confiscated opium in the port of Canton, war broke out. The conflict was one-sided, with the British bombarding Canton, seizing Hong Kong, and occupying Shanghai. . . . The Chinese empire surrendered its imperial monopoly on trade and agreed to free trade between Britain and China. China was forced to pay $21 million in war indemnities and as compensation for opium that it had confiscated. Finally, China ceded the port of Hong Kong to Britain as an entrepot for British exports--primarily opium." [Furtado: 1001 Days]