As World War Two loomed, the Falklands had already been prepared for some time.  A small squadron consisting of the cruisers Ajax and Exeter had been stationed in the Islands, making sweeps of the surrounding oceans for German raiders.

In December 1939 the Achilles joined the stationed ships and under Rear Admiral Harwood they left Port Stanley on a mission, which resulted in the Battle of the River Plate.

The Exeter was badly damaged, and limped back into Stanley harbour on the 16^th of December.  Of her original 600 crew, 64 had died, and 45 were wounded.  The ship was so badly damaged that the entire crew her to board in Stanley.  On the 22^nd of December Ajax and Achilles joined Exeter in Stanley harbour.

Following the Battle of the River Plate the admiralty established a naval office in the Falklands named HMS Poursuivant.  In 1942 an army battalion was sent out as a garrison force, which remained until the end of the war.