Another reason also is it only an effective weapon system if you can achieve concentration over an area for a prolongued period of time. In WWI, gas bombardments forced troops to wear their gas masks for hours. And it can only cover a certain amount of ground. It really isn't a good defensive type of weapon. I pointed out the Horse factor to Adolf on the "What if" thread. It seems he ignored it .

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For the first time I have seen "History" at close quarters,and I know that its actual process is very different from what is presented to Posterity. - WWI General Max Hoffman.

I'm the "Confederate with a pipe"!! LOL