<P> The following are some examples of improvised animal gas masks that were implemented: </P> <Ul> <Li> A dog wearing a gas mask in WWI . </Li> <Li> A WWI pigeon loft equipped with gas protection . </Li> </Ul> <Li> A dog wearing a gas mask in WWI . </Li> <Li> A WWI pigeon loft equipped with gas protection . </Li>

Who were the first to use poison gas in warfare