Lyric discussion by sheela_l 

Cover art for Mustard Gas lyrics by Dear Hunter, The

During WWI, mustard gas was commonly used by all sides involved.

This song is about war dehumanizes the enemy --- you're not slaughtering humans, you're slaughtering the enemy and just trying to survive another round of gas shells.

Disregarding the title, it could be about any major war since the beginning of the last century.