Dum-Dum Bullets

James W. Gerard.  My Four Years in Germany.  Late Ambassador to the German Imperial Court.  New York:  Grosset & Dunlap, 1917.

The first expandable bullet was invented around 1890 by Captain Neville Bertie-Clay at the Dum Dum arsenal near Calcutta.  Nasty things, they were banned by the Hague Convention in 1899. During World War I, the Germans accused the Belgians of using them, and the Belgians denied this.  To this day, no one seems to know which side was telling the truth.

Grolier Encyclopedia.  1957.