In 1930 the question of the replacement of Dunedin and Diomede, the two cruisers then on loan to the New Zealand Division of the Royal Navy, was under consideration, but it was only after several delays and not until September 1936 that the first arrived. She was the light cruiser Achilles (7,030 tons of the Leander class, built by Cammell Laird of Birkenhead and completed on 10 October 1933. Ships of this class were 554 ½ ft long, 55 ft beam, with engines developing 72,000 h.p. which through four shafts gave a speed of 32 ½ knots. As originally armed, the cruisers had eight 6 in. and four 4 in. guns, with two quadruple 21 in. torpedo tubes and a seaplane. When she was refitted in 1943, the Achilles was given six 6 in. and eight 4 in. guns.

Achilles earned her niche in New Zealand history when, with the Ajax and Exeter, she took part in the destruction of the Admiral Graf Spee at the Battle of the River Plate on 13 December 1939. The ship was hit several times. She shared in a wide variety of operations mostly in the Pacific until she was hit by a bomb from a Japanese aircraft in January 1943 and was sent to England for a refit. By that time she had steamed 246,000 miles on war activities. She returned to the Pacific for the remainder of the war, but was handed back to the Royal Navy in 1946. In 1948 she was sold to India and renamed Delhi.