Javelin or 'J' Class Destroyer
(profile contributed by Justin "LooseCannon" Riggir)

Two views of HMS Javelin


Part of a destroyer-flotilla at sea

Destroyers were built for speed and attack, and as such had no armour. Their light guns enabled them to engage other destroyers attacking their fleet, however in addition they were armed with torpedoes to engage any and all surface ships, including battleships.

Prior to the Second World War the destroyer-flotillas of the Royal Navy were organised into tactical units of eight each, with a ninth slightly enlarged type accommodating the senior officer of the flotilla, known as Captain (Destroyers), or Captain (D). As the policy had been to build one flotilla each year and to allocate each flotilla an initial letter, the standard fleet types built between 1926 and 1935 were known as the 'A to I' Classes, sturdy two-funnelled boats armed with four 4.7 inch guns and two quadruple sets of twenty one inch torpedo tubes. They were actually little different from the older 'V and W' Class dating from 1917, but two experimental prototypes built in 1926, the Amazon and Ambuscade, had introduced some improvements in detail. By 1936 the big French, Japanese and Italian ships were so obviously superior to the standard British destroyer that there was increasing pressure both inside and outside the Royal Navy to build a larger and better armed destroyer. The result was the 'Tribal' Class, with double the armament of the previous 'I' Class, but only four torpedo tubes. The opportunity was also taken to abolish the rather clumsy idea of having a ninth vessel as leader, because recent tactical exercises had indicated that the normal flotilla was too unwieldy, and that divisions of four destroyers each were ideal in action. The solution was quite simple, to alter the internal accommodation of the standard destroyer (as the 'Tribals' were bigger there was more space available) to make room for Captain (D) and his clerical and communications staff. If the leader became overcrowded extra personnel were transferred to other destroyers in the flotilla.

The next class of destroyers was a more positive step forward. By introducing a new stronger form of longitudinal construction the Admiralty was able to reduce the size, increase torpedo armament to ten tubes, and sacrifice only one twin gun-mounting. This more balanced design was known as the 'J' or Javelin Class, and a further innovation made them the first single funnelled destroyers, as two improved boilers gave the same power as three of the old type in the 'Tribals'. Both these classes rectified a serious omission in previous destroyers by having a four-barrelled two pounder (40 mm) pom-pom for close range aircraft defense. At last small ships had some defense against dive bombers, and the weapon remained standard throughout World War II. A disadvantage of these new destroyers was the Admiralty's failure to produce a workable high-angle gun-mounting for the main armament. The new expensive and weighty twin 4.7 inch mount in the 'Tribals' and Javelins could elevate only to forty degrees, which allowed it to fire only at distant aircraft formations. The reason was partly financial, in that the Naval Estimates did not allocate enough money to Research and Development on small ship fire-control and AA gun design, and partly due to discouraging experience with the high-angle eight inch gun of the 1920s.

The next class of destroyers were a repeat of the 'J' Class, The eight 'K' Class, of which the Kelly would in due course become the most famous. Following the alphabetical system, the 'L' Class were enlarged versions in which the main fault was rectified by mounting a dual-purpose main armament. The destroyers which resulted were among the most handsome ever built, with large gunhouses, however the gun-mounting and its fire-control were not entirely successful. Additionally, the cost of each unit rose alarmingly, and the Admiralty wisely decided to return to the 'J' design after only sixteen of the bigger ships had been ordered. At the outbreak of war only a few of the 'Js' had been finished, and it was not until 1942 before the last of the 1939 programme, the 'N' Class, were completed. During this period the decision had been made to adopt the 'J' design as the basis for a standard wartime design, to be known as the 'Emergency' design.

Destroyers saw much patrol work in the early months of the war, however their first taste of real action was in the Norwegian campaign in the spring of 1940, when the Home Fleet covered first the Anglo-French force's landing, and then its withdrawal. Norway gave the Royal Navy its first rude lesson in the potency of bombing, and an immediate result was that the destroyers with two banks of torpedo tubes lost the after one in favour of a three inch or four inch AA gun, while the 'Tribals' received a twin four inch mount in place of an after 4.7 inch mount.

Since 1918 the standard caibre destroyer gun had been the 4.7 inch, and there was also an anti-aircraft gun of this calibre, used in the aircraft carriers Courageous and Glorious and the battleships Nelson and Rodney. Extensive ballistics tests had led to a large increase in the weight of the 4.7 inch shell, however before the war it had been decided to change to a new calibre of 4.5 inch, in order to standardise calibres with the army. The ballistics of the 4.5 inch dual-purpose gun were even more favourable. The first version was a twin high-angle mounting for aircraft carriers and depot ships, and during the war a single barrelled version was produced for destroyers which is still in service.

From 1937 the standard light anti-aircraft mounting for small ships was the twin four inch, a weapon with nearly ninety degrees of elevation which proved very successful against aircraft, and during the war was even thought good enough to be the main armament for destroyers. However in 1939 the air menace was not sufficient for it to displace the low-angle guns being mounted in destroyers, a mistake which was to have dire repercussions. Older ships had single four inch anti-aircraft guns, which were not as effective, mainly because the mounting did not allow fast traverse.

The eight-barrelled pom-pom had been introduced in 1927 as a defense against dive bombers, and with its eight belt-fed guns pumping out projectiles at a prodigious rate it was the most effective weapon of its kind. A four-barrelled version was introduced for small ships, with unfortunately only half the rate of fire. These were supplemented with the Swiss 20 mm Oerlikon heavy machine gun, and the quadruple 0.5 inch machine gun which unfortunately suffered from frequent jamming.

In 1939 the Royal Navy was still using a torpedo which had been in service for twenty years. This torpedo had been improved with the addition of a magnetic exploder which would set off a torpedo underneath a target and produce far greater damage. As it increased the lethalness of the torpedo and its chance of scoring a hit, the magnetic pistol was very critical, however it had the weakness that it could be influenced by the earth's magnetic field if the torpedo ran too deep. The counter-measure was discovered to be degaussing, or electric neutralisation of the target ship's magnetic field, and in order to counter this the magnetic pistol had to be set to very sensitive levels.

The eight-strong 'J' Class were commissioned between June 10 and September 12, 1939 and consisted of Jackal, Jaguar, Janus, Javelin, Jersey, Jervis, Juno and Jupiter.

The eight-strong 'K' Class were commissioned between August 23 and December 21, 1939 and consisted of Kandahar, Kashmir, Kelly, Kelvin, Khartoum, Kimberly, Kingston and Kipling.

The eight-strong 'N' Class were commissioned between November 4, 1940 and October 30, 1942 and consisted of Napier, Nepal, Nerissa, Nestor, Nezim, Noble, Nompariel and Norman. Although these ships were the property of the Royal Navy, they were manned, commissioned and operated by the Royal Australian Navy with the exceptions of Nerissa which was transferred to Poland and renamed Piorun, Noble and Nompariel which were transferred to the Netherlands and respectively renamed van Galen and Tjerk Hiddes.

Specifications
Displacement: 2,376 tons standard
Dimensions: 356 (o.a.) x 35 x 9 feet
Propulsion: 2 boilers, 40,000 hp, 36 knots
Oil Fired: 5,500 miles at 15 knots
Armament: 6 x 4.7 inch guns (3 x 2) , 4 x 2 pdr AA guns (1 x4) , 8 x 0.5 inch AA guns (2 x 4) , 2 x 5 21 inch Torpedo Tubes
Crew: 183

Sources: Navies of World War Two by Antony Preston, Destroyers of World War II by M.J. Whitely and Australian and New Zealand Warships 1914 to 1945 by R. Gillett.

Links: The Worlds Warships - An extensive site on Warships both past and present