The 'dum-dum' was a British military bullet developed for use in India - at the Dum-Dum Arsenal - on the North West Frontier in the late 1890s.

The dum-dum comprised a jacketed .303 bullet with the jacket nose open to expose its lead core.  The aim was to improve the bullet's effectiveness by increasing its expansion upon impact.

The phrase 'dum-dum' was later taken to include any soft-nosed or hollow pointed bullet.  The Hague Convention of 1899 outlawed the use of dum-dum bullets during warfare.

During the First World War the Belgian government faced German charges of having used dum-dum bullets in battle.  Kaiser Wilhelm II wrote a telegram to U.S. President Woodrow Wilson on 7 September 1914 protesting such use; the Belgians strongly denied the Kaiser's charges.