Apparently, there were plans made on both sides during the ACW to break the stalemate, including 1 Union plan to utilise chlorine gas-filled shells in 1864, which was rejected by Lincoln, Grant, Sherman and other high-ranking Northern military leaders as being outside the rules of civilised warfare. But, WI the Union hadn't had such moral scruples on means of war- how would an ACW with chem and bio weapons have looked ? The horrors of WWI visited earlier ?