Germans began using poison gas on World War I battlefields, and if soldiers breathed in the gas, they might die slowly and painfully. An American scientist discovered that a charcoal made from the pits of stone fruits (peaches, plums, cherries) and the shells of certain nuts (walnuts, hickory nuts) could be used in gas masks to stop the effects of poison gas. Peach pits and other pits were collected by the millions to make this charcoal.