The use of chlorine gas against an unprotected enemy by the German Army in World War I on April 22, 1915 marked a new era in modern warfare. Chlorine gas dispensed from commercial cylinders into allied trenches on a favorable breeze. The allied troops ran for life from potent choking gas. The results 5000 allied causalities, sixty allied guns and enormous quantities of allied supplies captured. But the Germans were unprepared for the complete success of the attack. The allies soon developed respirators which gave complete protection against Chlorine. Later in July 1917, Germans introduced Mustard gas, one of the most important chemical agents in World War I. The new agent was not only toxic by inhalation, but it also attacked the skin by vesicant action, both as liquid droplets and vapor. In the period immediately prior to World War II, a series of phosphorous containing nerve poisons were discovered in Germany. One pf these Tabun and other Sarin which was more toxic was produced in pilot plant quantities. After World War II other nerve agents called Vagents were developed by US, which produce causalities not only by inhalation but also by skin absorption of very small Quantities of agent. With the advent of nuclear weapons Chemical Weapons were regarded as 2nd tier. But when they were used in Iran-Iraq war in 1990effects of Chemical weapons were realized. Saddam Hussein launched a large-scale chemical weapons attack against Iraq's Kurdish population in the late 1980s, killing thousands. On at least 10 occasions, Saddam Hussein's military forces have attacked Iranian and Kurdish targets with combinations of mustard gas and nerve agents through the use of aerial bombs, 122-millimeter rockets, and conventional artillery shells. Saddam Hussein continues his efforts to develop chemical weapons: Gaps identified by UNSCOM in Iraqi accounting and current production capabilities strongly suggest that Iraq maintains stockpiles of chemical agents, probably VX, sarin, cyclosarin and mustard.