Bioweapons do work.
I'd invite you to research Unit 731 of the Imperial Japanese Army. They used anthrax, plague and typhoid with frightening efficiency in parts of China during WWII. Estimates are 250K civilian fatalities just during TESTING. They buried literally tons of material in China and Korea before leaving; the strains of plague that were developed are still roaming around parts of Asia Major and being a problem today.
Dispersal systems are easy enough. Do you know how a flameless tear gas grenade works- same principles apply. The Japanese built and stocked ceramic canisters that could be released by artillery, aircraft or balloon, that would carry bubonic infected fleas and blood meal. Put a few black powder charges on the outside and mount an pressure altimeter if you want to air burst, otherwise just let if break on impact. Testing in hyperbaric chambers indicated that if you sent the fleas on a trans-Pacific flight under a balloon, then detonated them, 70% of them would get to the ground alive. They had plans to deploy them on the trade winds, but also by submarine launched balloons, and by sea plane launched from submarines. For anthrax, they used the same systems, just packed with spores wrapped in leather and laced with a nutrient broth. The only one that 731 couldn't really deploy other than by saboteurs was typhoid, although they had packed cannisters with it with the intent of targeting water supplies.
The trick is not killing yourself in the process of making them, and your delivery system, same as chemical weapons. And the Japanese were able to do it in the late 1930s and early 1940s, using hand made delivery systems. The only reason they didn't use them is.... Luck. Blind, pure, random luck is the only reason why the Allies had to dispose of this material, rather than having it used on us.
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-IronRaven
When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.