Chemical warfare agents: weapons of mass destruction or psychological threats?

In the last century, the deliberate use of chemical warfare agents not only inflicted mass casualties, but also had remarkable psychological consequences on the public opinion. A summary on the historical background of the most relevant kinds of aggressives and on their physical and chemical features is here reported and the main advantages and drawbacks linked to the use of chemical weapons in warfare actions or in terrorist attack at the beginning of the 21st century are discussed.