Blue Cross (chemical warfare)

Blue Cross (German: Blaukreuz) is a World War I chemical warfare agent consisting of diphenylchloroarsine (DA, Clark I), diphenylcyanoarsine (CDA, Clark II), ethyldichloroarsine (Dick), and/or methyldichloroarsine (Methyldick).

Clark I was initially used with Green Cross munitions; however for the first time it was used as a standalone agent in the night from July 10 to July 11, 1917, at Nieuwpoort, Belgium, during Operation Strandfest.

The artillery munition contained a large amount of glass spheres closed with a cork and sealed with trinitrotoluene (TNT).

Depending on the caliber, the munition contained 7–120 kg (15–265 lb) of the agent.

"Blue Cross" is also a generic World War I German marking for artillery shells with chemical payload affecting the upper respiratory tract.