This book is open access under a CC BY-NC 2.5 license.
On April 22, 1915, the German military released 150 tons of
chlorine gas at Ypres, Belgium. Carried by a long-awaited wind,
the chlorine cloud passed within a few minutes through the
British and French trenches, leaving behind at least 1,000 dead
and 4,000 injured. This chemical attack, which amounted to the
first use of a weapon of mass destruction, marks a turning point