21 August

1914

 * - Belgians forced to abandon their trenches at Namur.
 * Battle of Charleroi, between Mons and the Meuse, between French and Germans begins.
 * British move towards Mons.
 * - East Prussia: Advance of Second Army under Samsonov; occupation (August 21-23) of Allenstein, Neidenburg, Soldau, Johannisburg, etc.
 * No - South Africa invaded by German troops.

1915

 * - Second British Suvla attack (Gallipoli) on Anafarta fails.
 * No - German Fleet retires from Riga, disembarkation having failed.
 * - British Government declares cotton absolute contraband.