> because not having it mandatory led to infection waves and in the army that's even worse than in genpop
It also makes a stupidly-obvious tactic viable for the enemy.
It also makes a stupidly-obvious tactic viable for the enemy.
There is also the legend of sieging cities by catapulting diseased cows over the city walls. And if anyone knows the citation for that story, I'd love to see it.
Smallpox is a can of worms. But if you learn your enemy are idiots and don't have a flu vaccine, and you know your own forces do, I don't think you're going to get yourself sanctioned by your trade partners for exposing them to the flu. It will take out a statistically-measurable fraction of their troops, at a predictable interval, something you can plan to exploit with manoeuvre.
[1] https://en.wikipedia.org/wiki/History_of_biological_warfare#...