Destroyers are small warships (defined in the London Treaty of 1930 as being
no more than 1,850 tons), and armed with light weapons (guns of calibre no more
than 5.1 inches (130 mm)). In the British Royal Navy during World War II a ship
must also be fitted with torpedo tubes to be classed as a destroyer. They are
usually equipped for anti-submarine work, although some may alternatively be
equipped for minelaying operations.
Before World War II, new British destroyers were generally designated as
fleet destroyers, for work in support of the main fleet, which includes cruisers
and capital ships. Experience during the war lead to older destroyers often
being refitted and re-designated as escort destroyers (principally because older
destroyers lacked the speed of modern warships) and used for less glamorous
tasks such as convoy escort. The need for new specialist escort destroyers was
recognised, however, and these were also built during the war. The J class ships
are fleet destroyers, equipped for anti-submarine work.
Eight ships formed the J class (HMS Jervis as the flotilla leader, with the
others being HMS Jersey, HMS Jaguar, HMS Juno, HMS Jupiter, HMS Janus, HMS
Jackal, and HMS Javelin). They mainly served in the Mediterranean, and were
fitted with improved anti-aircraft armament compared to all previous British
destroyers. Nevertheless, (as with all small ships) they were extremely
vulnerable to air attack and later fleet destroyers tended to have anti-aircraft
armament that was better still. Only two ships survived the war, with five being
sunk before the end of 1942.
Despite the heavy losses of J class it was generally accepted that the design
was sound, and formed the basis for the 'emergency' designs that followed. A
total of 124 ships entered service as variations on the J class design, although
28 of these were completed after the end of hostilities.
The naval treaties between the wars had a significant effect on the design of
all warships. Weight limitations forced all naval powers to focus on weight
saving designs, bringing significant advances in several areas, such as advanced
propulsion systems and dual purpose weaponry (to be used in both surface and air
actions). The previous destroyer class - the Tribal class - were very much
larger than all other existing British destroyers, with a correspondingly
greater cost to build. The J class was intended to be a compromise, smaller and
cheaper than the Tribal class and yet with comparable speed and armament.
The J class were fitted with a total of six main guns and 10 torpedo tubes,
compared to the Tribal class with eight main guns and four torpedo tubes. This
increase in torpedo tubes represented a significant improvement in the
capabilities of the ship over the Tribal class, giving them a bigger punch
against capital ships. The reduction in main guns from eight to six was in
practice not significant, and as most British destroyers were only armed with
four guns the J class were considered to be heavily armed.
There had long been a desire to produce dual purpose guns for destroyers
which could be used both against aircraft and against surface targets. The
Admiralty was having considerable trouble developing a high-angle gun mounting,
and eventually it was decided to retain the low angle mount, which was limited
to a maximum of 40 degrees elevation. As with the Tribal class, each mount was
fitted with twin 4.7 inch (119 mm) guns. After considerable debate within the
Admiralty the aft gun was designed to train in a forward position, which
resulted in a blind spot over the stern of about 20 degrees whilst providing for
easier engagement of targets ahead. This decision represented the traditional
favour of offensive action over defensive measures. These guns were capable of
firing 10 rounds per minute each, with the rounds weighing 50 pounds (22.8 kg).
For air defence a four barrelled pom-pom was fitted. This at last gave
British destroyers some defence against dive-bombers, as they fired 115 rounds
per minute per barrel, and were effective out to 1100 metres (1203 yards).
Finally, eight 0.5 inch (13 mm) machineguns were installed in two mounts of four
guns each, although these were found to be prone to jamming.
For the anti-submarine role the ships were fitted with asdic and depth
charges. Asdic was a standard feature of British destroyers at this time. It was
effective out to about 2500 yards (2286 metres), although high speed and bad
weather both adversely affected its operation. Generally asdic was ineffective
if the ship was travelling above about 18 knots, and was unable to detect
anything within about 200 yards (183 metres) of the ship. Two racks of depth
charges were provided at the stern of the ships, as well as two depth charge
throwers on either side. Depth charges had to explode within about 20 feet (6.1
metres) of a submarine to breach its hull, and in the initial stages of the war
the British depth charges' maximum setting was over 100 feet (30 metres)
shallower than the maximum depth that a U-boat could dive to.
To protect the fleet from mines provision for a two speed destroyer sweep (TSDS)
was fitted to all but HMS Jervis, who as the flotilla leader had increased
accommodation for staff which reduced the space available at the stern of the
vessel.
The J class was the first to have only a single funnel, with improvements in
boiler design allowing the ships to be fitted with two more powerful boilers
rather than the three fitted to the previous Tribal class destroyers, with the
net power output being similar.
Longitudinal framing was chosen for the J class which, when combined with
electric arc welding, allowed the ship to be built more easily. Transverse
frames were still required around the machinery spaces however, to provide the
required structural support.
A destroyer's primary assets were speed and manoeuvrability. As with all
destroyers, no attempt was made to provide armour. This was because the amount
required to protect the ship from enemy weapons would result in a prohibitive
increase in weight, greatly reducing speed whilst increasing the size of the
ship (effectively turning the destroyer in to a very poorly armed cruiser).
There was some discontent when it was found that the J class were only
slightly smaller than the Tribal class (356.5 feet compared to 377 feet for the
Tribals), had fewer main guns (six compared to eight), and yet cost more to
build (£390,000 each compared to £340,000). Their performance silenced the
critics, and the basic hull form was used in many future variants.
It was originally intended that destroyers operate in groups of nine, with
eight ships under the control of one Captain (Destroyers), normally known as
Captain (D), in a ninth (larger) vessel. This arrangement was found to be
difficult to control in exercises just before the war, and tactical units of
four destroyers were seen to be more flexible. It was thus decided to build
eight J class ships, with the ninth (HMS Jubilant) being cancelled before
building began. This also reduced the cost and simplified the creation of
destroyer fleets as considerable effort was needed to create the single special
larger vessel for Captain (D) and his staff. Modifications to the ships were made during the war, following the general
trend of improving anti aircraft armament and providing radar capability
There is a tradition in shipbuilding of finding a design that works, then
modifying it for other newer ships so that the best of the old can be combined
with new knowledge. Evolution rather than revolution is the watchword. The
reasons for this are complex, but given the unpredictable nature of the sea, the
time and cost of construction, the difficulty of predicting performance for a
new design (still a problem today), the need for more destroyers quickly, the
inability to build a prototype for testing, the difficulty of future
modifications and the potential consequences of failure it can perhaps be
understood why many subsequent fleet destroyers adopted a slightly simplified
version of the J class hull form.
Although the variants listed below were all different in detail from the J
class, with later models incorporating hard-won war experience, they were
essentially J class ships. They all had the same power plant and basic hull
form, the same speed and similar main weapons (generally with slightly reduced
guns to speed construction and reduce cost). Often anti-submarine capability was
increased, along with anti-aircraft armament, and the greater weight made them
sit lower in the water (with increased displacement and reduced freeboard).
The next class to be built after the J class, the K class, were repeats of
the J class, except that TSDS was not fitted. There were eight vessels (HMS
Kelly as the flotilla leader, with HMS Kandahar, HMS Kashmir, HMS Kelvin,
HMS Khartoum, HMS Kimberly, HMS Kingston and HMS Kipling).
After experimenting with larger destroyers it was decided to revert to the
basic J class design. The resulting N class incorporated the modifications
already in the J class ships, with a four inch anti aircraft gun replacing the
aft torpedo tubes, two additional 20 mm anti aircraft guns and two twin 0.5 inch
machineguns. In all apart from HMAS Norman 20 mm guns were fitted in
place of the quadruple 0.5 inch machineguns (HMAS Norman was modified
later). They were all built with both air warning and air ranging radar.
Eight ships were built, with the Royal Australian Navy receiving HMAS
Napier, HMAS Nestor, HMAS Nizam and HMAS Norman, the Royal
Netherlands Navy receiving the Noble and the Nonpareil (renamed
the Van Galen and the Tjerk Hiddes), the Polish navy receiving the
Nerissa (renamed as Piorun) and only HMS Nepal being manned
by the British.
The Q class combined the armament of the O class with the hull of the J
class. They had four 4.7 inch guns, two depth charge mortars, three depth charge
racks, one four barrelled pom-pom, six single barrelled 20 mm anti aircraft
guns, two 0.303 inch machine guns, and two banks of four 21 inch torpedo tubes.
Both air ranging and air warning radar was fitted as standard, as well as asdic.
As fewer guns than the standard J class were mounted these ships had increased
bunkers at the expense of main gun ammunition, considerably improving endurance. Fleet destroyers are designed to act in support of a fleet, providing a
screen around high value ships. Prior to the outbreak of the war the Admiralty
had emphasised the role of the destroyer in the fleet action. British warships
thus spent the pre-war years preparing for 'the next Jutland', although this
time the enemy was seen to be the Japanese rather than the Germans.
There were eight Q class ships, which were manned by Royal Navy and Royal
Australian Navy personnel (
HMAS Quilliam
as flotilla leader, with HMAS Queenborough, HMAS Quadrant, HMAS Quail, HMAS
Quality, HMAS Quentin, HMAS Quiberon and HMAS Quickmatch).
Operational Use
Whilst the fleet was at sea destroyers were expected to prevent submarines
getting in range to attack cruisers, capital ships or aircraft carriers. Once
battle was joined they were expected to prevent enemy destroyers closing to
engage the larger ships with torpedoes, and (if ordered) to themselves close
with larger enemy ships and attack them with their torpedoes. The torpedo tubes
carried by destroyers made them a considerable threat to capital ships, and
their high speed and manoeuvrability made them difficult to hit with the
slow-training main guns of capital ships. However, a single hit from a capital
ship was liable to put a destroyer out of action.
Destroyers were also used when larger ships could not be risked, and were
described by one British Admiral as being 'expendable'. They were often used for
scouting waters which were feared to contain mines, submarines or other hazards,
or for work very close to shore (which might expose the ships to increased
chance of bombardment or air attack).
The J and K classes were heavily involved in action in the Mediterranean
(where most of the losses occurred), although they also served against the
Japanese later in the war. Only two of the J class survived the war, with much
of the losses occurring before the end of 1942. The K class fared little better
than the J class, and again only two survived the war. All the K class losses
occurred before the end of 1942.
The Mediterranean represented a particularly difficult challenge as an
understanding between Britain and France had allocated the Mediterranean to the
French. It was expected that France would neutralise any threat there with their
fleet (which was equal to the Italian fleet), supported from bases on the south
coast of France. With the French capitulation Britain was forced in to
allocating scarce resources to respond to the additional threat, leaving the
Royal Navy very stretched across the globe. To make matters worse, the situation
in North Africa, the loss of Crete and the basing of German aircraft in Sicily
deprived British shipping of air cover whilst exposing them to the attention of
the Luftwaffe.
In this environment shipping losses were heavy, and destroyers were
especially vulnerable with their lack of armour and light air defence. To meet
this threat the air defence capability of all ships was improved rapidly and
radar was provided as soon as it became available.
The other variants of the J class had a much easier time as by the time they
entered service the balance of power had shifted firmly in the direction of the
Allies. With the 'emergency' shipbuilding programme The British fleet had been
considerably expanded, reducing the load on individual vessels and allowing more
force to be brought to bear at any one time. Technological improvements (most
notably HF/DF and radar) had been fitted as standard, thus removing some of the
hazardous scouting work from the destroyer fleet and allowing information to be
gathered in a much safer manner. Anti aircraft armament had been upgraded and
the Axis no longer had air superiority. Only five of the other variants were
lost before the end of the war.
The ships served all over the world, more often in fleet work than in a
convoy escort role. Elements served in the Pacific, Atlantic, North Sea,
Mediterranean, South China Sea and Indian Ocean.