Leander-class Light Cruisers

The Leander-class was a group of eight light cruisers built for the Royal Navy during the 1930s, which saw extensive service during the Second World War. They were constructed in two groups: five of the Leander group, which were destined for the Royal Navy, and a further three of the Amphion group which were later transferred to the Royal Australian Navy. Two units, the Achilles and Leander, would later join the New Zealand Division of the Royal Navy, making New Zealand a 2-cruiser station, a number the archipelago would maintain until the 60s. The British and New Zealand vessels were named after figures from classical mythology, while the Australian ships were named after Australian cities.

Following the London Naval Conference of 1930, Britain was permitted to add another 91,000 tons of cruisers to its fleet. This addition was crucial, as all existing British light cruiser designs dated back to the First World War. Meanwhile, potential adversaries such as Japan and Italy were developing increasingly advanced and formidable designs.

Initially, the Admiralty aimed to distribute this additional tonnage across 14 cruisers of the same class, each with a standard displacement of 6,500 tons. Britain’s goal was to maintain a fleet of 70 cruisers. However, the finalized design of the Leander-class cruisers exceeded initial expectations, with a standard displacement of 7,200 long tons. As a result, only eight Leander-class ships were ordered, with other classes developed to utilize the remaining permitted tonnage.

The York-class was an important source of inspiration for the Leander-class. They basically had the same hull shape, containing a lengthy forecastle ending mid-way and a roofed superstructure. The compartmentalization also largely followed that of the York-class cruisers. One defining element of the Leander-class was their single truncated funnel. The Amphion group, however, would feature a more traditional two funnel set up later.  

During the building process, Britain sought ways to further reduce the weight of the units. Consequently, a lot more welding was used in the construction of the later sisters of the class. This paid off, as the standard displacement of the later HMS Orion was 340 tons less than the lead ship, HMS Leander. 

The Leander-class cruisers were armed with eight BL 6-inch guns mounted in twin turrets, with two turrets positioned forward and two aft. This design was a significant innovation, as earlier Royal Navy light cruisers typically featured guns mounted in single shields. The turrets offered better protection for the gun crews against splinters and adverse weather conditions.

The secondary armament consisted of four high-angle QF 4-inch Mk V naval guns, later upgraded to the more advanced Mk XVI variant. These 4-inch guns were highly effective against attacking aircraft. For close-range combat and additional anti-aircraft defense, the Leanders were equipped with 0.5-inch Vickers machine guns in quadruple mounts.

Like most British cruisers of the time, the Leander-class ships were capable of launching torpedo attacks, utilizing two banks of quadruple 21-inch torpedo tubes. Additionally, they carried two catapult-launched Fairey Seafox aircraft, which enhanced their reconnaissance and spotting capabilities. These Seafox seaplanes were later replaced by the more advanced and versatile Supermarine Walrus.

The primary role of the Leander-class cruisers was to protect commerce flowing to Britain from all corners of the British Empire. To perform this role effectively, the Leander-class needed to be fast. Admiralty 3-drum boilers provided steam to four Parsons single-reduction geared steam turbines, which converted thermal energy into kinetic energy, driving four propeller shafts.

The Leander group featured six Admiralty 3-drum boilers housed in boiler rooms grouped together within the ship. This configuration allowed for the distinct single funnel design. In contrast, the later Amphion group had only four boilers in separated boiler rooms, resulting in Australian units having two funnels instead of one.

The propulsion system of the Leander-class generated 72,000 shaft horsepower (shp), enabling a top speed of 32.5 knots. This made them slightly faster than their German counterparts of the time but slower than contemporary Italian and Japanese light cruisers of the early 1930s. With fuel tanks providing a maximum range of 10,610 kilometers at a cruising speed of 13 knots, the Leander-class cruisers could easily traverse the Atlantic.

As a light cruiser, the Leander-class had relatively weak armor, designed primarily to protect against the armament of destroyers. The class carried a total of 845 tons of armor (for comparison, the York-class heavy cruisers had around 1,400 tons).

Key protection details included:

• Magazine box: 3 inches of armor.
• Main deck: 1 inch of armor.
• Turrets: 1 inch of armor.

The machinery and rudder were left unprotected, and the belt armor was relatively thin. 

Olivier Goossens