The Battle of the River Plate was fought in the South Atlantic on 13 December 1939 as the first naval battle of the Second World War. The Kriegsmarine heavy cruiser , commanded by Captain Hans Langsdorff, engaged a Royal Navy squadron, commanded by Commodore Henry Harwood, comprising the light cruisers , (on loan to the New Zealand Division) and the heavy cruiser .
Graf Spee had sailed into the South Atlantic in August 1939, before the war began, and had begun commerce raiding after receiving the appropriate authorisation on 26 September 1939. Harwood's squadron was one of several search groups sent in pursuit by the British Admiralty and sighted Graf Spee off the estuary of the River Plate near the coasts of Argentina and Uruguay.
In the ensuing battle, Exeter was severely damaged and forced to retire, making for the Falklands; Ajax and Achilles suffered moderate damage. Damage to Graf Spee, although not extensive, was critical because her fuel system was crippled. Ajax and Achilles shadowed the German ship until she entered the port of Montevideo, the capital of neutral Uruguay, to effect urgent repairs. Langsdorff was told that his stay could not be extended beyond 72 hours. Apparently believing that the British had gathered a superior force to await his departure, he ordered for the ship to be scuttled. Three days later, Langsdorff killed himself.
Admiral Graf Spee had been at sea at the start of the Second World War in September 1939 and had sunk several merchantmen in the Indian Ocean and South Atlantic Ocean without loss of life because of her captain's policy of taking all crews on board before sinking the victim.
The Royal Navy assembled nine forces to search for the surface raider: Force G, the South American Cruiser Squadron, comprised the heavy cruiser of with eight guns in four turrets, the heavy cruiser HMS Exeter of with six guns in three turrets, and two light cruisers, HMS Ajax and Achilles, both of with eight guns. Although technically a heavy cruiser because of the calibre of her guns, Exeter was a scaled-down version of the County class.