'Second World War at Sea'
Part II: Mine Warfare
Ships, Subs and Aircraft
By Steven Ford High and
Kristin Ann High
is conducted by ships and aircraft, although
in the period covered by SWWAS
aircraft may only sow mines, not sweep them.
Mine-warfare ships may be classed as belonging
to one of four types:
- Dedicated fleet auxiliaries, including
minelayers, minesweepers, and mine warfare
craft that combine both layer-and sweeper
capabilities — SWWAS ship types ML,
MS, & AM.
- Converted obsolete fleet destroyers, escort
destroyers, and light cruisers — SWWAS
ship types DM, DMS, CM, and CMS.
- Modified fleet destroyers and, occasionally,
destroyer leaders or light cruisers, mounting
mining apparatus in place of A/S weapons
or torpedoes — SWWAS ship types DD,
DL, and CL.
- Submarines of all types — SWWAS
ship type SS — carrying mines in place
of torpedoes, torpedo reloads, fuel, or
possibly all three.
Each of these four types has capabilities,
advantages, and liabilities associated with
their employment in the mine warfare role.
Lastly, aircraft play a prominent part in
offensive mining operations.
U.S. Army minelayer Mayback.
(MLs, MSs, AMs)
Dedicated mine warfare ships — mine
warfare auxiliaries — are the most efficient
ships for minelaying or mine sweeping, the
moreso as their crews have extensive experience
with handling mines. Mine warfare auxiliaries
carry a greater load of mines, and place them
more accurately and more efficiently. Most
importantly for defensive minelaying, their
crews can be counted on to produce a well-charted
The combination of technical features and
crew expertise makes mine warfare auxiliaries
excellent choices for defensive work, mining
or sweeping friendly ports, yards, shore facilities,
and invasion beaches. One of their principal
drawbacks is their lack of speed and defensive
armament. These factors make dedicated mine
warfare auxiliaries difficult to operate in
contested or enemy waters, unless they are
protected and screened by warships.
Converted Obsolete Warships
(DMs, DMSs, CMs)
Another drawback is the expense of producing
and operating ships dedicated to mine warfare.
For many nations, modern dedicated mine warfare
craft are simply a luxury they cannot, or
will not, afford. For such nations, mine warfare
craft are rebuilt or reconstructed from other
ships, such as trawlers, sloops, and tugs.
These ships tend to be slow, vulnerable, and
difficult to sail in open waters.
Converted warships — obsolete or obsolescent
DEs, DDs, and CLs — are often permanently
modified to perform minelaying or mine sweeping
missions. Converted warships are something
of a compromise between the mine warfare auxiliary
and the modified fleet destroyer. They are
faster, better armed and better protected
than dedicated mine warfare auxiliaries. Because
they are usually older and have all been modified
to carry mines and minelaying gear, or mine
detection and sweeping gear, converted warships
do not possess the same firepower and speed
as the modified fleet destroyer. The principal
advantages of converted warships are their
relative economy, and their suitability for
tasks other than mine warfare.
Modified Fleet Destroyers,
Destroyer Leaders and Light Cruisers (DDs,
DLs and CLs)
Destroyer and minelayer USS Gwin,
DD-772 and DM-33.
The best offensive minelayer is also the
most expensive and most jealously guarded
— a modern fleet destroyer (DD). Swift,
well armed and well protected against submarine,
surface, and air attack, fleet destroyers
are potent weapons. The multiplicity of their
roles — they are scouts, shadowers,
submarine and MTB hunters, plane guards, convoy
escorts, and fleet escorts — gives some
idea of the demand for these workhorses.
To employ the fleet’s DDs on minelaying
missions is usually seen by the fleet commander
as a diversion of strength from the main effort
— finding and sinking the enemy’s
surface and submarine forces. Worse, a DD
modified to carry and lay mines has to land
a significant amount of its normal warload
— usually ASW weapons and torpedo armament.
Without these weapons, the DD is less effective
in its primary roles.
Unfortunately for the fleet commander, the
speed of fleet destroyers makes them effective
offensive minelayers. They can run at high
speed deep into enemy-controlled waters under
cover of night, sow their mines in likely
places, and run back to their forward bases
before dawn. Their minefields are nowhere
near as good as those of the other ships used
for minelaying operations, but the fleet destroyer’s
speed gives them the key element of surprise.
Their minefields might only damage a ship,
yet by sowing their mines deep in what had
been safe waters, they cause disruption and
instill caution in the enemy. On the other
hand, a minefield sown by fleet destroyers,
being unexpected, could reap high rewards,
and this only served to increase the demand
for DDs modified for offensive minelaying.
The fact that yard time was required to put
on and take off mine warfare fittings also
served to make conversions rather one-sided
— a DD might be modified for mine laying,
and not be refitted for normal duties until
it was docked for damages or in need of routine
refit in the yards.
Offensive minelaying became an established
fleet destroyer task in the Second World War.
While the first modifications were carried
out in the yards on a trial basis, with each
fit being unique and requiring highly-skilled
ship fitters, by the middle years of the Second
World War, even the famous American Fletcher-class
DDs and their follow-on Allen M. Sumner-class
and Gearing-class DDs had “minelaying
kits” mass produced for them; the kits
were standardized and could easily be installed
in the yards or even by a destroyer tender,
and be removed in the same way, as-needed.
Larger DDs fit for flagship duty — sometimes
called destroyer leaders (DLs) — or
some of the more modern, faster light cruisers
(CLs) were also sometimes modified for mining
missions, in the same manner as fleet destroyers.
The stealthiest of all minelayers is the
submarine. From the beginning of both wars,
submarines were used to lay minefields. Like
the fleet destroyer, employment of submarines
on minelaying missions was generally seen
as a diversion of resources from the vital
mission — attacking the enemy merchant
fleet. Nevertheless, submarines enjoyed the
supreme advantage of stealth, and their minelaying
capabilities were superior to those of the
fleet destroyer. The principal disadvantage
to employing a submarine as a minelayer was
again similar to the problems of employing
a fleet destroyer, the mines had to be taken
on in place of torpedoes and fuel, reducing
patrol time and limiting the possibilities
of attacking convoys — or warships —
On the other hand, submarine minefields were
even more likely to achieve surprise than
those sown by fleet destroyers, because the
submarine could hide in daylight, and need
not use speed to avoid detection. The British
Battleship HMS Nelson — flagship
of the home fleet and one of only two British
battleships not laid down before the Great
War in service at the time — struck
a U-boat-layed mine on 4th December, 1939,
and was drydocked for four months.
Fairey Swordfish often carried massive
mines in place of the usual torpedo.
During the Second World War, all the major
belligerents employed aircraft to lay mines.
The mines were carried aboard bombers or naval
strike aircraft. The famous Fairey Swordfish
and its younger stablemate, the Fairey Albacore,
could each carry a single 1,800-pound sea-mine
in place of the 18” aerial torpedo they
normally carried. Land-based level bombers
were generally more effective at sowing minefields
than carrier aircraft. Not only could they
usually carry more mines, they could also
operate at greater ranges, without exposing
valuable aircraft carriers to danger. They
were the only alternative for the Italian
and German navies, neither of which succeeded
in commissioning an aircraft carrier of any
sort. Land-based bombers could also use other
bombing raids as cover, breaking off to drop
their parachute-equipped sea-mines in rivers
and ship channels without drawing the same
attention a lone flight of mine laying aircraft
The major drawbacks to employing aircraft
in offensive mine warfare are accuracy and
density. The “simple” act of dropping
bombs on target in combat had turned out to
be much more difficult than anyone anticipated,
so dropping sea-mines over water at night
tended to be highly hit-or-miss affairs. Even
if all the aircraft on a mining mission dropped
on target, the density of the minefield was
not as heavy as that sown by surface ships
or submarines. It was due to a poorly dropped
sea-mine — it landed in the mud flats
of the Thames estuary — that the British
were able to take the superb German magnetic
mine apart, and thereby create effective countermeasures
Tune in next time for the
third and final installment in this series,
which presents variant rules and tables for
mine warfare in Second World War at Sea!
mines at work in Second World War at Sea: