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Whether we like it or not, we live in the shadow of Neville Chamberlain's Munich deal with Hitler. It must affect our perspective on any agreement of this nature. What we learned from Munich, though, was that deals do not finalize the results. What Hitler absolutely taught us was that what one says and even promises is not necessarily what one means.
The inadmissibility of chemical weapons on the battlefield was as early as 1899 an international principle of war. As is often pointed out, even Hitler -- himself the victim of a gas attack -- recoiled from their use in battle. The First World War scrubbed battle of its supposed virtues and in the place of heroism instituted the practical diplomacy of a League of Nations.