Little Sweeps ClearWay for Big Shipi

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Little Sweeps Clear Way for Big Shipi
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Like an aggressive boxer who car
ries the fight to his opponent, the
Navy's minesweepers have to "get in
there and mix it up." Any sweeperman will tell you you don't get rid of
a fleet tug-uss Sara (ATF 111).
Pirate and Pledge were lost during
the same operation in Wonsan har
bor, when they went down along
plete the clean-up of the retreat
enemy forces.
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What held them up? Mines. Linej
after line of what later proved to
with an ROK minesweeper, YMS
mines simply by sitting back and
an assorted variety of mines lay boM
516.
thinking about them.
That the plucky sweepers of the
Pacific Fleet nave actually been mix
ing it up in Korea will come as news
The Wonsan sweeping job, inci
dentally, offers a good example of
how the minesweeping Navy works.
tween the port's' docking area
the ships milling around 30 miles
in the Sea of Japan. In all, Navy oi
Here was the best harbor on North
mines lurkingin the 400 square mil
to no one. It is no coincidence that
Korea's east coast, a port which in
October 1950 had been taken by
ROK land forces. But for five days a
large Navy task force embarking
50,000 U. S. Army and Marine rein
of water. The handful of sweei
of the five U.S. Navy vessels sunk in
Korean operations, four have been
minesweepers. They were uss Mag
pie (AMS 25), uss Partridge (AMS
31), uss Pledge (AM 277) and uss
Pirate (AM 275). The fifth ship was
forcements had to remain outside the
harbor, unable to get ashore to com-
SA1LORS on board a minesweeper relax momentarily during search for
enemy mines off coast of Korea. In background are two other minesweepers.
cers estimated there were some 3'
had their work cut outfor them.
?|
The sweepers, three AMs and sixV<
AMSs, went to work. The job wa^jj
originally scheduled to take five days£
Plans were laid for the sweepers tr|
cut a path into Wonsan on a straight-;
line sweep from well out at sea t&
the inner harbor. By the afternoon of >
the first day, 10 October, part of|
the channel had been cleared andj
many mines had been swept and def<{
KfcSfflf
stroyed.
v|
Then a helicopter spotting for thel|
formation reported a' large "cabbage
patch" of mines just ahead. This
verified by dozens of mine ei
registering on Pledge's sonar. In.___,.
attempt toskirt this patch, the forma-^j
tion shifted its sweep to the northtoj
try another and perhaps less mine?|
ridden channel, a channel which had|
been used by the enemyonly a monthf.
before.
*|
For the next two days the 'copter!
continued its spotting. "Frogmen'!!
from UDT 12, riding in on rubbera
LCPRs, also helped to search. Ai\d|
uss Doyle (DMS 34), uss EndicoM
(DMS 35) and uss Diachenko (APJ$j
123) (the frogmen's "mother ship")3
helped the search in deeper waters^
looking for lurking mines.
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crack at the mines.
' fs
Next day, the Navy air arm took £jj
Trying a new form of mine war*';
fare, carrier-based Corsairs and Sfe^
raiders pulled off a "countermining;
strike." Dropping 100 bombs of thfei
1000-pound variety, they blasted^
away at a narrow sea channel nea$
flffe
the inner approaches through which;
the lead sweepers could pass.
.V
Soon after the air strike, the mine^i
sweepers, led by the flagship Pirat^
passed into the blasted area. The 80Q*:
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''"via
m
£fefr-i-is
31
ton, 185-foot, steel-hulled sweeper;
;^»!^t
Pirate was followed by sister ship^
Pledge and uss Incredible (AM 249ft
Little Redhead (AMS 34), a 21&tojpr|
136-foot, wooden-hulled sweepe^
2
ALL HAHQg
, [on"dannmg duty," ready to cast
_. erboard dan buoys orange-colored,
ig-topped, basketball-size buoys
sed to mark a swept channel.
JAlso in the formation was uss Kite
\MS 22), a sister ship of Redhead
[je was serving on "shotgun" duty
'er mission was to fire at severed
pes as they bobbed to the surface.
~s five-ship group was making a
ep against moored contact mines,
hese mines are what the type
t Navymen visualize when mines
» discussed. Two sections comprise
complete "assembly" of a mine,
st is the mine anchor assembly, a
|ge,square metal box which serves
&an anchor and houses cable re-
sing gear. This is connected by a
be anchor cable to the other part:
hpm studded, spherical case astbly containing the explosive.
|ijtact with one of the homs trig-
ms off the explosive—by way of a
Itonator and booster charge.
|The sweeper group altered course
LCVPs are being used for minesweeping operations in Korea. Here, a crew
rigs one of the small craft, for shallow water sweep off Chinnampo, Korea.
|theleft to pass between two islands and two 20 mms. She was soon joined
id entered unswept waters. Then
by Endicott and later by carrier air
^happened. Two horned mines — craft that were called into the fray.
jeircables severed by.the sweeping At length the enemy batteries were
gar—bobbed to the surface astern silenced for keeps.
^Pirate, Thenfour more bobbedup.
On October 18th the remaining
ledge, maneuvering through the sweepers had cut what they believed
jjd, cut three more. Incredible, also to be a clear channel to the beach.
|ithe thick of things, cut another
be 'copter then reported another
ge cabbage patch ahead. Soon af|this the sea beneath Pirate boiled
;engulfing her in a mass of spray.
jyess than a minute she went down.
Five LCVPs -from Diachenko had
helped in this endeavor. While the
'copter and recently arrived PBM
Mariners spotted mines for them,
frogmen tiding the LCVPs anchored
empty powder kegs near each mine
cable. This served to mark mine po
tledge stopped and lowered her sitions for the sweepers. In two days
jit to pick up survivors from her
|pr ship. To add to the confusion,
all moored mines within 15 feet of
the surface in the channel area had
been marked.
With but one hour of contact mine
sweeping left on the operation sched
ule, four AMSs were making a final
sweep when it happened again. Some
400 yards astern of Redhead the sea
rose up in an angry geyser. An influ
ence mine had been set off. A number
of mineswere then detonated in rapid
succession. One of the exploding
mines caught the ROK sweeper YMS
516, sending her to the bottom and
taking the lives of half of her crew.
This incident set D-day back sev-
iously undetected shore batteries
|an firing on the struggling swim-
Pledge opened up with her
H^-incher on the shore batteries,
a, the shore guns shifted their
|f from the men in the water to
*
ile all this was happening, 13
|e mines were floating around on
| surface; no telling how many
^moored mines lurked beneath,
bin minutes, Pledge struckone of
and also went down. Altoer, there were more than 90 cas
hes from the two ships, including
^ho went to their death with their
&s.
retaliation, uss Osprey (AMS
|moved in from a position further
award to work over the enemy
||e batteries with hersingle 40mm.
(EMBER 7952
NEAR MISS—Geyser of water eruptsfrom the surface of ocean as enemy pro
jectiles send UN minesweepers scurrying out of range. Nonewere damaged.
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FLAGTOPPED 'PIG' is hoisted aboard USS Mocking Bird (AMS 27). Right: Depressor is rigged on LCVP fofj
and pressure. Sweepermcn call these' pellers. When it does, its dia|
eral days. The whole channel now
had to be swept for influence mines.
"sinkers" or "mudders" because they
It took more than a week. As a result,
rest on the bottom instead of lurk
the amphibious force, including 21
transports and 15 LSTs had to mill
around in the Sea of Japan.
This demonstrates how mines can
foul up an operation and passively
defend a coast. And these are the
methods used to clear the way.
In the above narrative many terms.
have been bandied about which are
vibrates and closes the fatal'h
In a pressure mine, the negative
ing a few feet below the surface hke sure of a passing ship sucksV
phragm upward, closing the]
a contact mine. It doesn't take actual
Sweeping moored contacts
contact to set off an influence mine.
All you have to do is come close calls for plenty of "wire ropf
manship. Designs vary sftjr
enough to "influence" it.
type "influence" needed to set it off.
among types of mineswee|i
this is what a typical rig 1$
In a magnetic mine, the magnetic in
fluence of a passing ship induces cur
stern on both sides are Or'
The name of each' indicates the
Streaming out from the''in
sweeps. Aside
generally familiar only to men of the rent in a coiled rod within the mine "0"-type
short
span
of wire running^©
case.
This
closes
a
switch
triggers
off
"mine navy." Here is what some of
ship's
stem
to the water;'!t
the detonator, which in turn sets off
the more important terms mean.
thing
you
see
on the surfac
the explosive.
Influence mines (which made their
deadly debut in World War II)
generally come in one of three forms:
magnetic (met at Wonsan), acoustic
The acoustic mine utilizes a sim
ple hydrophone, an "artificial ear,"
set to hear a ship's engines or pro-
float or "pig." The pig res<i
airplane's wing-tip tank amj
a large, brightly colored rtfig?
It marks the outboard efjd
sweep rig. It also marks •*
FLOAT (OR PI6)
FLOAT PENDANT
OTTER
MINE
SWEEP WIRES
DEPRESSOR
water location of the ottt
blong, box-like device cfjjHi
curved fins set at an angr
frame. The fins hold the<
straight course about 35j|
port or starboard of
course.
'^
Spanning the pig an^
cable whose length 'Cffl!
depth of the sweep wifig
about 8/lOths of the dfy
water in the area 'being*
finned otter exerts a do«r
a forcewhichis balancedj
DIAGRAM shows minesweeper rigged to cut loose moored mines. Only
float shows on surface; pendant, otter, wires and depressor are under water.
ffi!&
ing pig. As a result, tho>w,
tached sweep wire do tj
the bottom but sweep a^
stant depth.
tL r't' Another pull - the horizontal pull
of the otter away from the ship's
heading—puts a strain on the actual
sweep wire, aserrated cable normally
about 300 fathoms long. Every 40
fathoms or so alone the sweep wire
are attached knife-like cable cutters
which snip the mooring cables hold
ing the mines underwater. At the in-
*1; board end, the sweep wire is con-
';..; nectcd to a depressor, a device simi-
'$ lar to the otter, which plows along
£ below the surface just aft of the ship
3 and which also helps hold the sweep
|?£: wire at its prescribed depth.
'"\- Aminesweeper rigged inthe rnan-
Vner described above cuts a channel
•^about 200 yards wide. Higher speed
'^sweepers such as the DMS class do
|not carry cable cutters on their sweep
LWires because the jagged nature of
pjie wire combined with the speed of
l]the ship is sufficient to saw through
T$the mine cable without further help.
^Should the sweep wire hit the mine
Jpable too late for the sawing process CREWMEN ready a motor launch for minesweeping work off Korea. The boat
|:to be effective, the mine cable is is especially rigged and equipped for sweeping operations in shallow waters.
^snipped off by a double-bladed cable
icutter on the outboard end of the
0&ie near the otter.
^ When a mine's cable is severed,
horn will explode it, of course, but covers a maximum area, but it fur
putting holes in buoyancy chamber nishes the least protection to the
fills the mine case with water. It then
fethe bouyancy chamber within the sinks to the bottom where it remains
sweepers.
In the "protective echelon" forma
hazard to sharks, ships' wayward tion, on the other hand, only the
|ubmerged mine case causes the mine aanchors
and anchor cables.
m pop up to the surface. As it bobs
sweeper leading the formation is ex
sweeping for contact mines, posed. Sweepers following in echelon
—nmd on the surface, the "shotgun" twoWhen
standard
are gener are covered by the sweep wire and
jgyeeper nearby sinks the floating ally used. The formations
first
is
the
open
eche otter of the sweeper ahead. Although
le with rifle fire or 20 mm. bursts,
itrary to general belief, it isn't
Jfcessary to hit a hom to do away
"ith a contact mine. A hit on the
lon" or "pigto pig" formation. In this it covers less area, it is a safer forma
one, the left otter of one sweeper tion.
trails the right otter of the sweeper
That's how they take care of
ahead (and to the left). This pattern moored contact mines. Dealing with
If gets underway with gear on board. Right: Crewmen prepare to drop 'pig' or float over minesweeo's side,
fMMBER 1952
^m
,»- t.-*" t" - '5 9 •*<» ^
to that created by a pneumal
breaking down a piece of city
ment.
Pressure mines can be set off?
towing weighted, expendable baif
across the suspected area. It may
a couple of barges, but it saves
and ships. Another method (usei
Japan after World War II) is to
old Liberty ships through the
The weight of barges and
ships sets up a pressure more n
equal to capital and service forci
ships. Bantamweight AMs and AMfe
don't have the necessaryweight (fffiiia
tunately for them) to detonate
mines.
.;•''•»
Tricky combinations can be set in
to influence mines. For example, afi'.^
USS GULL (AMS 16) swept area near Chinnampo for mines so U.N. forces
could stage a 'commando raid,' cutting enemy rail and supply lines.
influence type mines calls for entirely
water, creating a strong magnetic
different measures. Of course, naval
field which in turn "influences" the
vessels and many merchant ships
neutralize themselves in degaussing
coils which theoretically render the
vessels "magnetically neutral." This
magnetic mine to detonate itself.
Sweepers make several passes
when searching for magnetic mines
because mines oftentimes are set to
acoustic trigger can be rigged.to'-a^S
magnetic mine. Such a mine would '
lie dormant duringa magnetic sweep.
However, a ship with powerfuleD'.
gines and noisy propellers coming
along later would be crippled. Her J
noise would release the acoustic trig
ger and then —unless properly d«K
gaussed—her magnetism would set
off the deadly magnetic trigger. Sueli -;
method is not infallible, however, be
go off only after a ship has passed
are the problems facing the NayjftSji'
cause of the many magnetic vari
ables both in the ship's own mag
netic field and in the earth's mag
over them several times.
sweepermen.
Handling the other two types of in
fluence mines requires still other
detection and destruction are being -1
netic variation.
measures. Acoustic mines can be set
Strung out aft of a vessel engaged
in magnetic sweeping are large
cables. When the cables are in posi
tion, a powerful shipboard generator
is started. Powerful surges of current
move through the cables and the
off by increasing the noise level. An
electrically or hydraulically operated
"hammerbox" at the ship's bow just
below the watcrline can trigger them
However, new methods of mine, 'jjjj
developed ail the time. Since the out* *.|
break of war in Korea, a new type,','§
hghtweight sweeper has made its aj> ||
off by banging away. The hammer-
pearance. This is the minesweepiqgyS
boat (MSB). It evolved from LCV$;V®
which worked with special
box makes noise in a manner similar
weight minesweeping gear.
_'* i*
i ,fiTS^ -if'*, »»#•«:••"
SWEEPMEN on board an LCVP rig their 'pig' for sweeping operations. Another LCVP is already on the jobat
6
ALL Hi
r'^f'Sl
iv, MSBs, like LCVP minesweepers,
pire also designed to be carried to the
I'scene by a mother ship. More than
1^.50 MSBs are now in service or under
^^•rWW'^W^
Jrconstruction. These wooden-hulled
^•vessels are 57 feet long, have a 10-
§ knotspeedand a crewof seven. Other
| details: diesel engines, twin screws
tand very shallow draft. They are de
ll signed to work in areas too shallow
1:even for AMSs with their eight-and^ne-half foot drafts.
iSv In addition to the newly evolved
|MSBs, there are four well-established
'pes of active duty vessels serving
ithe mine navy. Largest ofthese are
^the high speed mine sweepers
|(DMSs) and light mine layers
^'(DMs). Both types were converted
prom World War II destroyers and
^retain their original names.
* Next largest are the fleet mine
'eepers (AMs). These ships are185
221 feet long, steel-hulled vessels
nth diesel and diesel-electric drives,
fcese and the smaller AMSs have
tndled the brunt ofthe Navy's mine
USS THOMPSON (DMS 38) sustained her second hit by Red coastal guns
in same area where she suffered her first battle damage over ayear ago.
DAIS Seeking Out Coast Target Sustains Second Hit
While standing off Songjin onthe lookout and talker, they reported the
teeping both in World War II and
east coast
ie Korean war.
Thompson (DMS38) sustainedher
second hit by Communist coastal
guns on 20 August. Enemy shells
killed three crewmen and injured
10.
'
'
Bycoincidence Thompson was in
the same area where on 14 June
guy-"
1951, she suffered her first battle
John M. Donnell, Jr., usn, one of
the same guns that had killed three
stepped outondeck tospottheloca
tion of the shore guns with his
|The high-bowed, 136-foot auxili'rymotor minesweepers (AMSs) are
fie Navy's largest wooden-hull vesMs, weighing in at 270 tons. Prior
1947 they were known as motor
nesweepers (YMSs). AMs and
Ss are the most numerous or
ie Force vessels, about 50 of each
s being in commission.
I'Minesweeping boats are not the
lly mine craft whose development
"i given a boost by Korean sweeplessons. The AMCU - mine hun—is another. A number of these
^.included in the 1952 conversion
Sgram, a few beingconverted from
iS-type craft and the others from
intry landing craft (LCI) types.
$y will carry explosive ordnance
"isal teams during anti-mine opions.
fc the Navy there are ships many
fes as large and three times as fast
pie great majority of sweepers.
Jflayman can tell you quite a few
of North Korea uss
other crewmen and wounded a like
number.
The high speed destroyer-mine
sweeper had only recently arrived
for her second tour. The previous
night, the ship had operated with
U.N. east coast blockade and escort
forces, firing on a rail bridge north
of Tanchon. Replenishing at day
light, she moved north to participate
in an air-spotted bombardment of
targets in Songjin.
"7 draw a blank. But every now
the next shell hit the flying bridge,
£ then—such as a Wonsan and
hampo —a mine field holds up
pperau'on and the'bigsteel jobs"
Br. move
in.
Then
the
little
ersbecome the most important
in the Navy.-W. J. Miller,
', USN.
VEMBER 1952
ing. That's why I figure I'm a lucky
Thompson's navigator, Ensign
glasses when there was an explosion.
He said, "It felt like someone was
pouring hot lead down my leg. I
shook my trousers a little and some
chunks of metal fell out."
uss Iowa (BB 61), flagship of the
Seventh Fleet, intercepted Thomp
son's report of action and steamed
to her assistance. The wounded
were quickly transferred and rushed
below to the battleship's modern
As she prepared to open fire on hospital where doctors worked
the target area, an enemy shell through the night. Iowa's doctors
splashed near her bow. Immediate
praised thework ofThompson's hos
ly the ship got underway at flank
speed, changing course frequently.
8|it minesweepers and you'll prob-
behind the fire control director. The
next shell hit where we were stand
damage and casualties during her
destroyer - minesweeper's
first Far Eastern tour, apparently by the
wounded, reported that he had
j| oilers and transports. Ask him
figs about destroyers, submarines,
first shell splash to the officer of the
deck. "Then," said Moore, "my
buddy grabbed me and pulled me
pital corpsmen for the first aid treat
ments given the casualties and of
Despite theevasive action, however,
Lieutenant (junior grade) Floyd H.
spraying shrapnel in the pilot house
and fire control platform.
One of the injured men, Joe R.
boarded the minesweeper by heli
Moore, SN, usn, said that he owes
his life to his buddy, Donald B.
Smith, SN, usn. While he and
Smith were on their GQ station as
Poteete, Jr., (MC), usn, when he
copter to ready the patients for
highline evacuation.
Other U.S. ships in the Korean
War which have been hit twice by
coastal gunfire are uss Helena (CA
75) and Osprey (AMS 28).
- , ' pi,