the singular most important tool Britishers used in something called “Opium War”.

I don't want to downplay the horror of opium, but the Opium War was a war.

The reason the British went to war is because the Qing were making progress getting rid of opium. The British needed their gunships to make sure the opium stuck. It wasn't that opium was such an impossible problem to combat, it's that the British navy beat them in two wars when they tried.