With war looming in August 1939 Germany, like Britain, took preparatory steps at sea. These included deploying the pocket battleships Deutschland and Admiral Graf Spee so they could attack seaborne commerce should war erupt. Commanded by Captain Hans Langsdorff, Graf Spee sailed from Wilhelmshaven on 24 August, five days before HMS Achilles left New Zealand. A support ship, the tanker Altmark, had left Germany on 2 August.
Langsdorff's orders were to cruise near the Cape Verde Islands until war began, then move into the South Atlantic to operate as a commerce raider. The aim was to disrupt enemy sea movements by creating doubt and uncertainty. Since repair or replenishment after a major engagement would be difficult, he was to avoid contact with enemy naval vessels.
After exercising near the Cape Verde Islands, Graf Spee was given the green light by Berlin to begin raiding operations on 26 September. Four days later, the warship claimed its first victim, sinking the British merchant vessel Clement. The British ship managed to broadcast a distress signal, the first indication that a German raider was operating in the area (although it was initially thought to be Admiral Scheer).
South America Division
In December 1939 the South America Division included the heavy cruisers HMS Exeter and Cumberland, displacing 8400 and 9700 tons respectively, and armed with six to eight 8-inch (203 mm) guns capable of firing 116-kilogram shells 17 kilometres. It also included the light cruiser Ajax, in which Harwood, from 28 October, flew his pennant as commodore of the division. Like Achilles, it displaced about 7000 tons and mounted eight 6-inch (152 mm) guns that fired 51-kg shells. The cruisers were capable of 31-32 knots.
Achilles joins the hunt
As a result, Achilles was ordered to quit its watchdog role along South America's west coast and proceed to the South Atlantic. After a steady passage, and refuelling at the Falkland Islands, Achilles reached the southern approaches of the River Plate on 26 October. It joined Commodore Henry (later Admiral Sir Henry) Harwood's South America Division, which had been transferred from the America and West Indies Station. The New Zealand ship joined the division's heavy cruisers HMS Exeter and Cumberland and the light cruiser Ajax in patrolling the Rio de Janeiro/River Plate area. The monotony was broken by a visit to Rio de Janeiro from 10 to 12 November, and then a long patrol north as far as the northern boundary of Brazil, which was reached on 2 December.
The next moves
Meanwhile, Langsdorff had headed around the Cape of Good Hope into the Indian Ocean, where he intercepted and destroyed a British tanker. He moved back into the South Atlantic on 20 November. On 2 December, in the eastern South Atlantic, the Graf Spee sank the Blue Star Line's Doric Star, bound from New Zealand to the United Kingdom with a cargo of frozen meat and wool.
The raider distress signal that the Doric Star managed to send alerted the Admiralty. British naval authorities pondered the raider's next move. It would clearly not stick around the area, but where would it go next? An important clue was received on 3 December when a distress message was picked up from the Shaw Savill and Albion steamer Tairoa. As this was west of the Doric Star's position, it appeared the German ship was heading for the east coast of South America.
Harwood was conscious of three focal points for British trade - the Falklands Islands, Rio de Janeiro and the River Plate - where a raider might expect rich pickings. He concluded that the River Plate was the most likely target and decided to concentrate his force there. Achilles, having returned from its patrol along the Brazilian coast, had arrived in Montevideo on 8 December. Ordered to sea the next day, it joined Ajax on the 10th. Although Cumberland, refitting in the Falklands, was unavailable, Exeter arrived to join the light cruisers at 6.30 a.m. on 12 December.
When smoke was spotted on the horizon at 6.14 a.m. next morning, and the ship was quickly identified as a pocket battleship, Harwood's guess was vindicated. But, as alarm rattlers alerted the crews, he had no time for self-satisfied reflection. Within minutes his division was in action.
