decided to upgrade her armament and fire-control systems. The bridge was rebuilt and enlarged to accommodate a second High-Angle Control System aft of the Director-Control Tower (DCT) on top of the bridge, her single four-inch AA guns were replaced with twin-gun mounts for Mark XVI guns of the same calibre and a pair of octuple mounts for two-pounder "pom-poms" were added abreast her aft superstructure. Enclosures ("tubs") for single Oerlikon guns were added to the roof of both 'B' and 'Y' turrets, but these weapons were never installed, because of shortages in production, and lighter tripod-mounted machine guns were substituted. The pole masts were replaced by stronger tripod masts because the Type 279 early-warning radar had separate transmitting and receiving aerials, one at each masthead. In addition, a Type 284 fire-control radar was fitted to the DCT. Construction and career Exeter, the fourth ship of her name to serve in the Royal Navy, was laid down on 1 August 1928, launched on 18 July 1929 and completed on 27 July 1931. The ship was then assigned to the 2nd Cruiser Squadron of the Atlantic Fleet, where she served between 1931 and 1933. In 1934 she was assigned to the America and West Indies Station and remained there, aside from a temporary deployment to the Mediterranean during the Abyssinian crisis of 1935–1936, until 1939. Second World War Battle of the River Plate At the outbreak of the Second World War, she formed part of the South American Division with the heavy cruiser , under Commodore Henry Harwood. The ship, commanded by Captain Frederick Bell, was assigned to Force G to hunt for German commerce raiders off the eastern coast of South America on 6 October 1939. Two months later, Harwood ordered Exeter and the light cruiser to rendezvous with his own off the mouth of the Río de la Plata, while HMS Cumberland was refitting in the Falkland Islands. The two other ships arrived on 12 December, and then the Admiral Graf Spee spotted the Exeter during the following morning. Captain Hans Langsdorff decided to engage the British and closed at full speed. The British doctrine on how to engage ships like the Admiral Graf Spee had been developed by Harwood in 1936 and specified that the British force act as two divisions. Following this procedure, Exeter operated as a division on her own while Achilles and Ajax formed the other,