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[The notes on this patrol are taken from an account by a British observer, con B. B. Lakin, RN, and give a relatively detached view of what happened and why.]

This patrol resulted in the infliction of the following damage on the enemy:

1 KUMA Class Cruiser 5,300
1 Tanker or Ore Ship 10,000
1 Engines-aft Merchant Ship 3,500
1 Sub Chaser or Patrol Boat 500
TOTAL 19,300 tons

A full outfit of 24 Mark XVIII 29-knot electric torpedoes were carried, and all were expended.

The percentage of hits scored was 25%. Duration of Patrol — 43 days. Distance steamed — 10,371 miles. Fuel used– 107,954 gallons.

19 July to 30 July. 1944. The writer joined the USS CROAKER at Pearl Harbor on 19 July. CROAKER is a standard 1500-ton fleet type U.S. submarine, built in 1943 by E.B. Company, Groton, CT. She was commissioned 21 April, 1944. Her serial number is 5-246, which indicates that she is the last of the thin-skinned boats, i.e., those having a pressure hull 5/8″ thickness and designed diving depth of 300 feet. Submarines built subsequent to this have had the hull thickness increased to 15/16″, giving them a diving depth of 500 feet. (As most of the patrol was spent in the Yellow Sea in depths of 25 to 30 fathoms, this disability was of rto great concern.) Another disadvantage she suffered by comparison with the later series boats was that the bridge structure had not been cut down in accordance with the n.odified design and consequently was the old fashioned, covered-wagon type with an unnecessary amount of top hamper, and having a lookout platform forming a roof over the greater part of the bridge. The wind deflector was inefficient by British standards, and the bridge deck a veritable menac·~ of pitfalls, obstructions, projections and blind spots, and a poor place from which to keep a lookout. The best that can be said is that one got used to it.

Just before sailing, a 40MM gun was mounted on the after deck of the bridge (cigarette deck), and consequently the starboard side of the bridge was largely occupied by a ready use ammunition locker for this gun (holding 84 rounds of ammunition in clips of four}, on top of which was rigged a canvas and tubular Metal bunk for the CODltnanding officer who used this every night in the patrol area. A single 20HM was mounted before the bridge, wtdch with the 4″, was u.anne:d throu~lt an access dool’ jn the cab (similar to older British 5-boats). There was no gun tower. A slightly newer pattern, of the usual 4″ gun, was mounted forward, having normal watertight tampion but with a different design of breech, which eliminated the waterproof box-cover over the firing mechanism. No great enthusiasm was shown for employing these weapons and in view of the extreme time taken to man them and to fire the first round (3 minutes), one can scarcely blame them.

The 20MM was kept in the ready position with a drum of ammunition in place while in the patrol area at night, and 40MM was manned on one occasion at night when it was thought possible that a patrol boat might be encountered in shallow water. During the passage-run, one 4″ gun action from submerged was practiced, and all automatic weapons were used in an engagement with a profusely bleeding whale which the ship had unintentionally rammed. The ship suffered no damage from the collision, and the whale none from the gunfire. Several mines were sighted which, according to the operation orders, should have been destroyed, but the Officer-of-the-Watch usually felt that no opportunity was offered. The submarine invariably zig-zagged while on the surface, using either a set zig plan or the Arma Course Clock.


This system was operated the entire patrol with the exception of periods of silent running. The remarkable difference in comfort that it made was only really apparent during those periods when it was not working. As an offshoot from the main air conditioning air supply, an extra unit was installed in the wardroom compartment just before sailing, as this part of the ship had previously been a dead spot in the ventilating and air cooling system. This unit produced a steady temperature of 50°F in officers quarters the entire patrol, during which times the battery temperature underneath was never less than 90°F and the gutside 0 sea water and air temperature between 80 and 84 F. u.s. submarine officers say that the improvement in the upkeep of electrical equipment since installing efficient air conditioning is most marked, and certainly the writer has never before seen a submarine that had so little internal sweating.

USS CROAKER sailed from Pearl Harbor at 1330 July 19th. A dive for trim, off Barber’s Point about an hour later did much to dispel any impression that these submarines are slow in diving, until the Diving Officer discovered that be bad been 15 tons heavy in his trim. The passage to Midway was uneventful except for sundry defects which cropped up. The steering failed, followed by the planes and both were put into hand. All power to the internal announcing systems and alarms failed and also a fuel line to one main engine parted. None of these was serious, and all easily rectified.

The ship arrived at ~~dway in the forenoon of 23 July. The Commanding Officer, Jack Lee, and the writer had a discussion with the Commanding Officers of TANG and SEALION, both submarines which had recently returned from Yellow Sea areas, the forme~ having sunk eight ships and the other five. They both reported sighting mostly unescorted single ships and gave an amount of useful information on the shipping routes. This personal encounter with those “last from school”, was most valuable.

The ship sailed again at 1730, escorted for the first 30 miles by two Navy Dive Bombers, whose value the writer was unable to see, and for the next week ran westward (roughly along the parallel of 30° N) on the surface at two engine speed (111.5 knots), using 70 gallons of fuel per engine per hour. Course steered was Great Circle which, over this distance, was not very appreciably shorter than tion dive sions the rhumb line, but was ordered by the operaorder for outgoing submarines. A practice was made every morning and on several cocathe ship dived for an hour in the afternoon.

During surface running, a total of six lookouts (each with 7 x 50 binoculars) and two Officers-of-the-Watch were always on the bridge, and watch was kept through one periscope. In addition, the Officers, including the writer, stood four hour watches, which he considered too long, and the lookouts rotated every hour. Two of the six were volunteers. The lookout was at all times very efficient and vigilant and there was an unofficially approved monetary scale of rewards for sightings.

About the second day out from Midway an epidemic of common coldes started and raged throughout the boat. Several men were off the duty list for a day, but a gargle and some tablets of APC (similar to Vegamin) induced a good sweat and soon cured them. The cause of this was probably the usual one, of lookouts wearing insufficient clothing on the bridge.

August 6. Shortly after coming to periscope depth, the alarm sounded and an attack was started on what appeared to be the fighting tops of three NAGATO class battleships. Unhappily, these were soon identified as fishing junks, a fairly natural mistake since the visibility inshore in the forenoon was inclined to be hazy and there was some mirage effect. A decision was made to patrol nearer the shore and this resulted, at 1630, in sighting a merchant ship at a range of 11,000 yargs. coming southward from Nagasaki, course of 175 , evidently altering course for navigational purposes only. When sighted, the submarine was fairly fine on the starboard bow, and probably over estimated the distance off track as she found herself later almost dead ahead at 3,000 yards, and was compelled to make an advancing turn away to port, which was accomplished all in good time, enabling her to fire four stern torpedoes set to 6 feet on tracks of 105° to 120°, at a range of BOO yards. All missed, which was as surprising as it was depressing, since this one looked in the bag, and the only reason the Commanding Officer had fired as many as four, was to make sure of getting a certain hit on the submarine’s first attack. The target was a 3,500 ton merchant ship in ballast, and it seems very probable that the torpedoes ran under, since conditions were perfect, being almost flat calm with a slight ripple. The target passed unconcernedly on its way, as likewise did the four electric torpedoes, which further contributed to their already invisible quality by not exploding at the end of the run.

The Commanding Officer was very loath to give up this ship, which had already cost four torpedoes, so when CROAKER found herself dead astern with the range still closing, he fired three single torpedoes at 1,500 yards on a 180° track (a questionable shot at the best of times, as the writer with some diffidence suggested). At any rate, the first torpedo which was fired while the submarine was still doing a good 17 knots leaped out of the water and settled down with a considerable bias to starboard. The next, fired after a reduction in speed, made a poor discharge too. It was discovered that the control party in the conning tower had fired, in error, the top tubes instead of the bottom, so the third torpedo was fired at about 2,100 yards range with about 7 knots headway on the ship. This appeared to run straight, but being trackless, one couldn’t tell. It missed also, and after that, the attack was abandoned.

Monday. August 7. At 1100, the Officer-ofthe-Watch sighted the mast and fighting top of a cruiser at 14,000 yards approaching from the southward at 14 knots. An exciting attack ensued in which several sharp turns had to be made as the target, an unescort~d 5,300-ton KUMA, was making large zigs every three or four minutes. Eventually the last four stern torpedoes were fired iL~ediately after taking a ping range of 1,000 yards on a 140° track. The Cruiser zigged away on firing, probably on the leg of his irregular zig plan, and after three minutes had elapsed ~jnce firing, hope of securin& a hit was slender, so the Commanding Officer raised the periscope to try and get another shot in from the bow tubes. He was just in time to see the entire stern and mainmast of the Cruiser disappear in a pillar of flame a~d smoke. She had providentially zigged back and caught the last torpedo of the salvo at the extreme end of its run (4,500 yards for electric torpedoes) • A lucky shot indeed! Pandemonj un1 ensued in the control room which was anyhow seething with people and cigarette smoke. The writer contributed a modest cheer to the general din, which was making it iJnpossible for the Diving Officer to be heard, and then was invited to inspect the target through the periscope. The Cruiser presented a very stirring sight, having €1l1’eady assumed a big list to starboard, and was awash U!J to tt•e after funnel. It was possible to see down the funnels and the crew were leaping over the side. The still and 16mm movie cameras were secured to the periscope and a number of pictures taken, (which were the first technicolor periscope movies of their kind). This operation was interrupted by the report of screws f’rom the south. Cameras were hastily removed, leaving the Commanding Officer with no eye piece for his first all around look. A patrol boat some miles away was headed towards us and an ~ircraft which appeared to be the sole escort of the Cruiser was cor.;naencing to search, so CROAKER Has taken deep to 300 feet, and shut off for depth changing.

For the next seven very swelter·ip.g hours the submorjue reo;ainecl deep while a spasmodic and unsystematic dropping of depth charges was carried out. Twenty-three depth charges in all were heard. At 1800, the submarine regained periscope depth. Nothing was in sight. After air conditioning, and fans were switched on, the boat began to cool orr, and its drooping occupants revived like wilting plants after a good watering.

Monday, August 14. While making the nightly excursion into the shallows. a radar pip appeared at a range of 17,000 yards at 0100, while off Cbosei To. This was tracked and overtaken, and its course and speed determined as 305° 8 knots, over a period of 60 minutes steady glotting. CROAKER at 18 knots gained a position 60 on the target’s port bow at a range of about 7,000 yards and then turned to starboard for a large track at 2,000 yards (which is the ideal combination usually sought by U.S. submarine Commanding Officers) . Thanks to the excellent radar plotting and TDC operation and a very good judgement on the Commanding Officer’s part, it was a remarkably well timed attack, and CROAKER arrived in position and slowed down on a steady course a few minutes before the gyro angles were most favorable for firing. The target, a 3,000-ton engines-aft merchant ship in ballast, obviously unaware of our presence, somewhat naturally assumed that she was safe when within a chain of islands and steamir~ in 7 fathoms of water. Four bow torpedoes were 0 fired on a 75 track at 1,500 yards range.

CROAKER turned to seaward immediately after firing and increased speed to 20 knots. One torpedo, only, hit, and that one right aft, blowing off the stern and bringing the target to a standstill, but showing no desire to sink. CROAKER turned around and approached the stopped ship, from which the crew were evacuating in a small boat. The Commanding Officer did not wish to approach near·er than 2, 000 yards to fire the coup de grace, but however some confusion arose in the conning tower about the gyro angle on the torpedo, (a straight shot seemed to present more of a problem to the fire control party than an angled one). By this time the submarine was deemed too close and the Commanding Officer pressed the firing key. The torpedo firing reservoir had not been charged, but on hearing the firing solenoid lift the TGM hastily charged it and the air started to eject the torpedo. Meanwhile, the swing on the ship was increasing and the Executive Officer had inquired and had been told not to fire, and had released his grip on the firing key. The impulse was cut off and the torpedo was left running, half out of the tube. By the time this catastrophe had been discovered and straightened out, the running time for the torpedo was nearly exhausted so it was jettisoned with a full impulse.

CROAKER then readvanced to finish off her prey with a certain acrimony on all sides. After some preliminary juggling for position the sixth torpedo was fired at the target and struck it in the stern about 20 feet forward of the first one and the ship rolled over and sank in under one minute. It was somewhat unfortunate for the crew that they, mystified no doubt by the CROAKER’s antics, should have elected to return alongside the ship at precisely the same moment as the torpedo.

Wednesday. August 16. Dived and patrolled submerged off Kakureppi Island. At about 2100, when the submarine was proceeding south some five miles off the shoal water, the radar got a contact at 11,200 yards on a small ship. CROAKER was astern on the starboard quarter and proceeded to overhaul at 18 1/2 knots, adjusting course to keep about 6,000 yards off track to make certain of being outside visibility range. The two plots and the TDC soon agreed on an enemy course of 190° speed 9 knots, and so when CROAKER was about 60° on the enemy’s starboard bow she turned 90° to port and ran in on a 90° track. There was no moon and it was a dark and starry night with the enemy against a rooky shoreline. He came in sight at 3,500 yards — a very low silhouette and appeared to be a 500-ton submarine chaser steering a steady course. CROAKER reduced to 7-8 knots and at a range-of 1,500 yards, fired a single electric torpedo set to two feet from the bow tube on a· 92° track, turning away on firing and increasing to twenty knots. The target’s length could not have been more than 150-180 feet, and the writer was extremely dubious about the success of such a shot, and so it was much to his amazement, and joy that, hardly had the submarine reached it’s “escape” course than there was a glorious explosion accompanied by a sheet of flame and burning debris, and the patrol boat disappeared from sight without a trace. It was a most spectacular hit, and an admirably timed and executed attack which was a triumph for the radar tracking party.

Thursdav, August 17. CROAKER continued to patrol southward on the surface. Between midnight and 0200 a phantom radar contact was chased. This frequently occurred during the patrol and the pip usually broke up, provine it to be a rain cloud, or else by its stationary position was eventually identified as one of the many islands which abounded in these waters. However, at 0215, a good sized ship was detected about 15,000 yards ahead and to the southeastward. The radar tracking party got busy and prgduced an enemy speed and course of 8 knots, 210 .The ship was evidently coast-crawling in the usual manner. CROAKER had some distance to make up, and not a great deal of time to spare as dawn broke at about 0350, so increased speed to 19 1/2 knots and commenced to overhaul at a distance of 6,000-7,000 yards off track. Radar then detected a zig to port by the enemy, and it was apparent that he was going to pass through a narrow channel between two groups of islands (Matsu To), the same channel where CROAKER had been cheated of a ship on Sunday, 13th, by the interference of the supposed patrol boat during the final stages of the approach. This time there was no other ship around and just sufficient time before daylight to run outside the islands to the starboard side of the channel and attack the ship as it emerged.

The submarine accordingly hauled out to starboard, passed the islands close on the port hand and swung to port as soon as it was clear to do so, steadying on a 90° track. The target, a large loaded engines-aft tanker or ore ship of about 10,000 tons, came into view at yards, and the submarine fired three torpedoes at 2,200 yards, confidently expecting, with the previous success on the PC boat fresh in mind, to get three hits. One torpedo ran erratic, and one hit only resulted, and that right forward, which merely reduced the enemy’s speed by four knots. Three more torpedoes (the last) were fired, allowing enemy speeds of 0, 2 1/2, and 5 knots. One hit right aft, and the ship oollapsed, rolled over and sank in a very few minutes. CROAKER retreated to seaward, all torpedoes expended, ar.d dived in 17 fathoms as dawn “‘as breaking over the nearby islands.

August 23- 31. On passaee from patrol area to Midway. For the first two days a head wind of force 4 and heavy seas were encountered, reducing the submarine’s speed by 2 1/2 to 3 knots, and making the bridge very wet. This appears to be caused by the large, unnecessarily wide upper deck casing which extends from beam to beam of the ship and serves no more useful purpose than is achieved by the narrow British variety. Many of the crew, several of whom had never been to sea before were prostrated with sea sickness during this period.


It has been mentioned before that CROAKER carried a full outfit of (24) MARK 18-1 electric torpedoes. The choioe of his torpedo out!’j t t’Ests with the ComiDanding Officer, and now that then early development troubles of electric torpedoes have been overcome, more and more CO’s are electing to use them entirely, and are willing to accept the slow speed for the greater advantages of invisibility. They rarely give trouble nowadays after they have been installed on board, and the regular maintenance, once a routine for charging the batteries has been arranged, is less than for an air torpedo.

The MARK 26 torpedo, mentioned in the last periodical report, has been tested and approved, and is in production. This has the same range as the MK 18-1 — 4,500 yards, but an increased speed of 45 knots. The propulsion is electric through a silver plate battery using salt water electrolyte, which does not enter the cells until the torpedo is fired.

In the opinion of the Submarine Command, the day of the air torpedo will definitely be over when experiments have been completed on another new torpedo, which is propelled by an enriched air cycle and whose exhaust is almost completely soluble in water. A torpedo of this type was contemplated in the early 30’s but the idea was never developed owing to the outbreak of the war. The present proposition will have a speed of 45 knots for 11,000 yards and carry a 1,100 lb. warhead. At the moment production of the MK 18 is about 300 per month, and insufficient to meet demands; preference in the issue of these is therefore given to submarines operating in areas where daytime attacks only are likely to be undertaken.

Depth setting policy is also under revision. It is now considered by a number of experienced and successful CO’s and by the Submarine Command, that torpedoes set to depths of 20 feet for merchant ships are needlessly deep and will not inflict as much damage on the ship as those set as shallow as weather conditions will permit, which on hitting increase the venting of the ship’s hull and add to the fire risk.


The reader could not have failed to not:ice the constant reference to radar in the narrative and the part it played in the success of the patrol. In fact, three out of the four ships sunk were detected by radar and it was largely due to the accurate information tha.t it gave, that the subsequent attacks were successful. Radar tracking or shadowir~t; forms a large part of the working up period, and a very competent team had been trained in CHOAKER, whose efficiency and productions of accurate enemy data impressed the writer. Small wonder that night surface attacks are preferred and practiced more than day submerged attacks, and in general are more skillfully executed. The night attack directed by radar is no longer the hit or miss, hurried browning shot affairs of yore. In fact the data obtained is based on continuous plotting with all guess work eliminated and is considerably more accurate than resulting from periscope observations.

This happy state of affairs will c~:ist just so long as the enemy persists in failing to “catch on” to radar, or at any rate to operate his present electronic equipment sufficiently well to con&titute a menace to submarines. When that happens, and the submarine is no longer able to penetrate screens or approach surface ships without being detected, it will have to rely on picking up the enemy before they are aware of his pr·esence (this :is probable since the enemy will be the larger target in most cases), t~en submergi~~ ahead of his estimated track and finishing off attack with the radar·-periscope combined with sound.

The SJ radar in CHOAKER functioned extremely well in spite of being the most hard worked unit in the ship. It went wrong only once, and then in a big way, requiring four·teen hours worlc by the combined teant of two electricians and the radar officer to coax it back to life.

The writer could not find himself in agreement with the amourt of smoking which took place in the submarine while djved, and the fact that the sounding of the battle stations alarm was regarded a~ a signal for· ever·y nen.ber of the crel-1 to start charging the air with nicotine. After several hours running, with air conditioning and the fans stopped, the air in the ship became foul.

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