It's curious to me that drugs, such a pertinent and widespread political issue in the 20th and 21st centuries - whether it's controversy over legalizing or prohibiting one within a country, trying to suppress their illegal trade, or interfering with another country by supplying them drugs - seem to have almost no impact on history prior to this point despite having been widely used since prehistory. I can't say I've ever heard about drug production, trade, addiction or policy in say, the medieval or classical eras (except, of course, for alcohol - but then, what makes it so unique?).
It seems absurd to picture a medieval villager going to his dealer to buy weed, but why? The drug existed, so why wouldn't it be grown, sold and used, and thus subject to the law and all the complications and conflict that we know come with drug trade and its regulation?
Something relevant to your question, as you await direct answers is that despite the name, Opium was in many ways a minor factor in the first Opium war, and the conflict was much less drug-related than many popular narratives portray.
An excellent explanation of the causes and context can be found in this answer written by u/enclavedmicrostate,
The same author also wrote this exceptional post on Opium in Chinese society, which touches on the arrow war and includes many interesting details and additional context.
As well as this post, which cover similar ground with additional details