What was the cause of the opium war in 1839-1842?

Between 1839 and 1842 British forces fought a war on behalf of drug traffickers. Their victory opened up the lucrative China trade to British merchants. This was all done with the full blessing of the British government.

two months after his defeat of napoleon bonaparte's colonial forces, jean-jacques dessalines proclaims the independence of saint-domingue, renaming it haiti after its original arawak name. in 1791, a slave revolt erupted on the french colony, and toussaint-louverture, a former slave, took control of the rebels.