There is morality in warfare, war slowly civilized in Europe during the Middle Ages and Christianity was a big reason for that. Tactics that would have been eff

There is morality in warfare, war slowly civilized in Europe during the Middle Ages and Christianity was a big reason for that. Tactics that would have been effective weren't used simply because it became unconscionable. The Crusades, and then the Napoleonic invasion of Russia, were both notable departures, and both saw militaries surprised when their adversaries used tactics that had long been banned in Europe. The French were not expecting the Russians to put the torch to their own lands so as to deny the French forage. It made the difference that led to the famous infographic. It's not unreasonable to think that nation-states refrain from biological warfare for moral reasons. As effective as they might be, the government using them wouldn't survive either due to politics or the hammer of the world coming down on them.