Huh? Are you talking about the opium wars where China was invaded by the British and forced to stop trying to combat their opium epidemic? I've never heard of an interpretation of events where China made opium illegal in an attempt to forestall invasion by Western powers.

"forced to stop trying to combat their opium epidemic" is a really euphemistic way of saying China banned opium inside their borders, so Britain invades China so Britain can sell opium to China.

It was a national security concern, insofar as smugglers bringing cocaine, heroin, and marijuana into the US via Mexico are a matter of national security for the US.

What's euphemistic about it? I used the same intensity words as your description (literally the same words, like "invaded") and mention a superset of the information (I asserted that the ban was primarily intended to combat their opium epidemic, as opposed to e.g. hurting British interests).

It's circular to bring up the US War on Drugs to support the argument that the opium wars were about national security, in response to a comment challenging whether the opium wars support the argument that the US War on Drugs is about national security. My whole point is that I'm skeptical of the case that either is about national security.

Another lesson in the unintended consequences of prohibition.

That's not really what's happening in this case.