Wasn't it tabun the nazis had, but were too afraid of retaliation in kind to actually use? I recall reading something along the lines of that Hitler might have won the war if he had used the new nerve agents he had developed on us.
I doubt he would have won. The US had the atomic bomb, or was extremely close. If Hitler did start using chemical warfare I have no doubt we would have just used Atomic Bombs on every major city/German outpost in a matter of days and nearly whiped out the German 'race'.
Physics trumps chemistry, in that particular case!