"As to the effectiveness of phosphorous and thermite against machine-gun nests, there is no recorded instance where our gas troops failed to silence German machine-gun nests once they were located...In the next war, no matter how soon it may occur, a deadly composition called Lewisite will be used with far more devastating effect than that of mustard gas."
To read this article is to understand what busy bees they must have been over at the U.S. Department of War within that year and a half following the close of the First World War. General Amos A. Fries and the lads attached to the Chemical Warfare Service had been applying much cranium power to all matters involving mustard gas, tear gas, Lewisite and White Phosphorus. Much of the post-war dollar was devoted to making ships impervious to gas attacks, masks and uniforms suited to withstand nerve agents and offensive aircraft capable of deploying chemical bombs.
Click here to read more about gas warfare during the First World War.
Click here to read about the new rules for warfare that were written as a result of the First World War - none of them pertain to poison gas.