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." [1001 Days]