The United States must improve its ability to defend its citizens and property against potential terrorist or "rogue state" attack with chemical weapons. As a military weapon, gas has been effective at causing casualties but has never been a "war winner." History shows that chemical weapons are most effective when used against an unprepared enemy that cannot retaliate in kind. The 1995 nerve agent attack in Tokyo was a "wake up call" for the United States to come to grips with the serious asymmetric threat from either rogue states or terrorists who could launch a devastating chemical attack on our homeland. This paper will trace the military history of chemical weapons and assess programs necessary to prevent, protect, and respond to a chemical WMD attack on the United States of America.