Leander-class cruiser (1931)

The Leander class was a class of eight light cruisers built for the Royal Navy in the early 1930s that saw service in World War II. They were named after mythological figures, and all ships were commissioned between 1933 and 1936. The three ships of the second group were sold to the Royal Australian Navy (RAN) before World War II and renamed after Australian cities.

Design
The Leander class was influenced by the York-class heavy cruiser, and was an attempt to better provide for the role of commerce protection. The 7,000-7,200 ton Leanders were armed with eight BL 6 inch Mk XXIII naval guns in twin turrets, two forward and two aft. Their secondary armament consisted of four QF 4 inch Mk V naval guns, which were later replaced by twin mountings for eight guns (the later QF 4 inch Mk XVI naval gun). Their anti-aircraft weaponry consisted of twelve 0.5 in Vickers machine guns in three quadruple mounts. They also shipped a bank of four 21 in torpedo tubes on each beam and provision was made in the design for carriage of two catapult-launched Fairey Seafox aircraft.

Speed was 32 kn, and 845 tons of armour was provided. The first five vessels did not contain dispersed machinery; the boiler rooms were arranged together and exhausted into a single funnel, a unique feature amongst British cruisers. This meant that damage amidships was more liable to disable all the boiler rooms.

Wartime modifications
During the war, significant modifications were made to the vessels. Various additional anti-aircraft armaments were added, and the two New Zealand vessels removed a turret to carry heavier 20 mm and 40 mm anti-aircraft guns in its place. Changes to the aircraft launching capability were reported, although use is unclear. Both Fairey Swordfish and Supermarine Walrus aircraft are reported to have been used by the class.

Leander group
Named after the character from Greek mythology. Loaned to New Zealand, commissioned as HMNZS Leander in September 1941. At the Battle of Kolombagara, Leander was heavily damaged by a Long Lance torpedo, causing many casualties, and sending the ship to repairs for two years.
 * Leander

Achilles was the second vessel loaned to New Zealand, commissioned as HMNZS Achilles in September 1941. She had earlier participated in the Battle of the River Plate. Achilles was sold to India in 1948, and was known as HMIS Delhi for a few years, then served as INS Delhi, until 1978.
 * Achilles, later HMIS/INS Delhi.

Ajax participated in the Battle of the River Plate. The town of Ajax, Ontario was named after the ship, with street names in the town named after members of the crew. Ajax also participated in the Battle of Cape Matapan and took part in shelling the mainland of Normandy during the beach landings.
 * Ajax

Manned by New Zealand crew, although not part of the Royal New Zealand Navy. Neptune was sunk by an Italian mine off the coast of Tripoli.
 * Neptune

Orion participated in the evacuation of Crete in 1941 and was heavily damaged.
 * Orion

Modified Leander group
The last three ships of the class, referred to as the "Modified Leander", "Amphion", or "Perth" class, had their machinery and propulsion equipment organised in two self-contained units (separated fore and aft), allowing the ship to continue operating if one set was damaged. The two exhaust funnels, one for each machinery space, gave the modified ships a different profile from the early Leanders, which had a single funnel. To cover the separate machinery spaces, the side armour was extended from 84 to 141 ft, negating the weight reduction created by the separation. During design, it was planned to modify the forward-most and aft-most 6-inch turrets to be fitted with three guns instead of two, but the plan was cancelled when it was determined that the required alterations would cause several negative side effects, including reducing the ship's top speed and causing problems with effective fire control. All three ships were sold to the RAN, Sydney while under construction and Perth and Hobart after a few years of British service.

Completed 1936 as HMS Amphion and transferred to the RAN as HMAS Perth in 1939. She operated with British ships in the Battle of the Mediterranean, participating in the Battle of Cape Matapan in March 1941. Lost in the Battle of Sunda Strait in early 1942.
 * Perth (ex-Amphion)

Completed 1936 as HMS Apollo and transferred to the RAN in 1938 as HMAS Hobart, she took part in the East African Campaign, the Battle of the Coral Sea and provided fire support at Guadalcanal. After being badly damaged by a torpedo strike in 1943, she returned to action in the Philippines landings (1944), followed by the Borneo and Aitape-Wewak campaigns. She was put into reserve after the war and was not decommissioned until 1962.
 * Hobart (ex-Apollo)

Laid down as HMS Phaeton, the ship was acquired by the RAN, launched as HMAS Sydney and was commissioned in 1935. Also involved in the Mediterranean campaign. Sydney sank the Italian cruiser Bartolomeo Colleoni at the Battle of Cape Spada in 1940. Later that year, Sydney took part in the Battle of Cape Matapan and Battle of Calabria, sinking two Italian destroyers, the Espero and Zeffiro. In 1941, off Western Australia, Sydney encountered the German auxiliary cruiser Kormoran; the two ships destroyed each other and Sydney was lost with all hands; the wrecks of both ships were located in 2008.
 * Sydney (ex-Phaeton)