by Peter Sasgen
While the Spadefish was outfitted with FM sonar, her sonar men underwent special training to learn how to operate the gear and how to interpret those green blobs and bells: Were they mines, kelp, or fish? If they got it wrong, the Spadefish wouldn’t stand much of a chance if she got tangled up in a row of Japanese mines.
As for her crew of motor macs, electrician’s mates, and the like, they weren’t impressed with FM sonar and its purported ability to locate mines. So far it hadn’t worked as advertised, when it worked at all. And anyway, hunting mines was a job for minesweepers, not submarines. Things went so badly with it that the equipment finally had to be removed for repairs at UCWDR’s lab, after which it was delivered back to Mare Island, where it caught up with the Spadefish completing her fitting out for war patrols. As scuttlebutt spread through the sub force that more submarines were going to be equipped with FM sonar, sub sailors took a dim view of what might be in store for them. Back in Pearl, Lockwood sifted through the daily reports submitted by Dr. Harnwell, Dr. Henderson, and by SubPac’s liaison officer in San Diego, who had his ear to the submarine grapevine. Lockwood discovered just how controversial this new gadget was and how little enthusiasm for it there was among submarine sailors. Lockwood knew that he had to convince both officers and enlisted men to get on board with FM sonar or there’d be no mission to the Sea of Japan. The only way to do that was to perfect the damned thing and then prove that it worked. If he couldn’t do it, he’d never put together a task force of submarines to tackle the job he had in mind.
The Spadefisharrived at the submarine base at Pearl Harbor in late June. No sooner had she tied up than Lockwood and Voge crossed the brow for a conference with Underwood. The two senior officers peppered the skipper with questions about his experience with FM sonar in tests at San Diego.
Underwood’s report wasn’t particularly encouraging. Tests of the Spadefish’s equipment conducted on dummy mines off the coast of California had been disappointing. FM sonar had failed to register mine contacts visually on the PPI scope or audibly by hell’s bells. Sometimes the unit couldn’t detect targets at all or had a hard time differentiating between solid objects and schools of fish. It wasn’t reliable, said Underwood. Vacuum tubes burned out and wiring overheated. Repairs often took hours. If Lockwood expected submariners to trust this gadget when it came time to locate real mines, he had another thing coming. This wasn’t what Lockwood and Voge wanted to hear, but they took the news in stride. Lockwood the optimist believed that he, his men, and the scientists at UCDWR were pioneers in the business of submarine mine hunting and, like any new venture that relied on unproven technologies, it would take time to flush the bugs and gremlins out of the sonar units coming from UCDWR’s labs.
In the event, UCDWR technicians who had gone on ahead to Pearl to meet the Spadefish gave her FM sonar a thorough going-over. They also supervised some needed voyage repairs—heavy seas had bent the deck-mounted transducer’s shaft—after which they pronounced the system ready for duty.
Lockwood put to sea in the Spadefish on July 13 to experience firsthand a full-scale test of FM sonar, not on a live minefield but on a dummy minefield planted by the Navy’s mine force in the deep waters off Barbers Point, Oahu.
Employing recent intelligence about Japanese mines and minefields collected by JICPOA (ICPOA had been renamed Joint Intelligence Center, Pacific Ocean Areas), the mine force had sown the dummies to replicate an enemy field. Lockwood believed that submarines attempting a penetration of the Sea of Japan would encounter such fields and that familiarity with their layout would provide the submariners the experience and confidence to make a clean run through them.
The Japanese employed a moored spherical, horned contact mine known as a Type 93. Weighing 1,500 pounds, it was filled with 220 pounds of TNT plus a pusher, usually powered aluminum, to increase the mine’s explosive force. Later models had up to nine sulfuric acid-filled horns protruding from the mine’s cast-iron surface. When a ship hit a horn, it would break open, releasing acid, which energized a battery and set off the detonator. Japanese mines were usually sown in two or three rows across shipping lanes or, in the case of the Sea of Japan, across straits of entry, the rows spaced four hundred to a thousand yards apart. A gap of seventy-five to a hundred yards separated each mine from its neighbors to prevent an explosion from setting off the other mines in the string by chain reaction.
The mines making up a field were generally planted no deeper than a hundred feet, often in three tiers ranging from ten feet to forty feet to seventy feet. A minefield’s effectiveness is reduced somewhat by “mine dip,” which occurs when deep-water currents push cable-moored mines in the direction of the current flow several feet lower than their planted depth. This so-called “dip gap” gives passing ships a greater margin of safety than they would otherwise have had. Such was the case when Ray Bass ran the Plunger through La Pérouse Strait during that early foray into the Sea of Japan. As Bass discovered, mine dip may have accounted for the fact that he and his crew were still alive and their sub in one piece. Even so, Bass’s blind run through La Pérouse was thought to be far too dangerous for any submarine to attempt it again. Experience would prove otherwise.
As for those floaters often sighted by patrolling submarines, international agreements stipulated that mines were to be armed only when the weight and tug on the mooring spindle armed the detonator. Otherwise the mine was supposed to self-sanitize, that is, render itself harmless. No one trusted the Japanese to abide by such agreements, so submarines gave floating mines a wide berth. Moored or not, the assumption was that the Japanese had planted thousands of mines in waters bordering Japan to protect the home islands from invasion from the sea. As long as U.S. submarines operated in those mined waters, Lockwood had to hope that FM sonar, aside from facilitating a raid on the Sea of Japan, would reduce the risks that mines posed to submarines engaged in regular war patrols.
Lockwood’s ride on the Spadefish was an opportunity to gauge FM sonar’s sensitivity and accuracy for himself. UCDWR technicians, some stooped with fatigue from the late nights spent tearing apart, repairing, testing, and reassembling the Spadefish’s unit, declared it was fully functional again. Lockwood, and especially Underwood, expected to see a vast improvement over its performance in California.
Approaching the dummy minefield off Oahu, Underwood gave the order to submerge: “Clear the bridge! Dive! Dive!”
Two honks of the Klaxon diving alarm sent the men into action. Lockwood and the four lookouts, followed by Underwood, scrambled down the ladder from the bridge to the conning tower below, the eight-foot-by-twelve-foot horizontal steel cylinder set above the ship’s control room. Every inch of space inside was taken up with periscopes, FM sonar gear, radar scope, sonar stand, and the TDC. Underwood, his exec, the quartermaster of the watch, the helmsman, sonarman, telephone talkers, and now ComSubPac shouldered around one another trying to make room.
The OOD, the last man down, slammed the hatch shut and dogged it. “Hatch secured, sir.”
The hammer of diesel engines ceased as propulsion shifted to the batteries. A litany of orders and repeat-backs resounded between the conning tower and control room. “All ahead full! Rudder amidships! Five-degree down bubble!” In the control room the chief of the watch promptly closed the outboard and inboard engine exhaust valves and main induction. Scanning the red-and-green-lit Christmas tree hull opening indicator panel, the chief reported, “Green board; pressure in the boat.” The main ballast tank vents popped open with a whoosh! as the chief, his hands a blur, pulled the hydraulic vent valve control levers open one after another. Seawater flooding her ballast tanks, the Spadefish started to submerge. A landlubber might have thought he was witnessing pure chaos but in fact it was a series of practiced evolutions required to submerge the Spadefish in thirty seconds.
Underwood, looking down into the control room through the open hatch in the conning tower’s deck, ordered, “Make your depth six-five feet.”
The divi
ng officer confirmed the order. “Six-five feet, aye.” Lockwood, the deck under his feet angling down, held on and leaned away from the dive. He was in his element, among fellow submariners aboard a fleet sub.
The two men seated at the diving stand in the control room muscled the big nickel-plated wheels controlling the Spadefish’s bow and stern planes. As the Spadefish approached sixty-five feet—periscope depth—the diving officer asked for two-thirds speed, then ordered, “Blow negative to the mark!” Dewatering negative tank restored the sub’s neutral buoyancy and helped trim the ship for submerged operations. Then, “Ease your bubble.”
Underwood motioned for the periscope. The quartermaster yanked the hydraulic control lever in the overhead. The scope hummed out of its well, jerked to a stop at its upper limit. Underwood made a quick 360-degree scan. Satisfied that the area was clear of ships, he turned the scope to the marker buoys dead ahead, where the minelayers had sown a dummy field. “Coming up on the mine plant.”
Satisfied that he’d demonstrated for his three-star boss how tight a ship he ran, Underwood ordered, “All ahead one-third. Stand by on FM sonar.”
Lockwood hovered near the PPI scope, watching over the operator’s shoulder. He saw a circular glass screen with concentric rings, like ripples from a stone dropped into a pond. The rings indicated ranges from one hundred yards to several thousand yards. Bearing lines, like the spokes of a wagon wheel, extended across the scope’s face to all points of the compass. The circles and spokes allowed an operator to plot the position of any mine contacts relative to the position of the Spadefish. A thin, luminous line swept continuously around the circumference of the scope: If the sonar beam made contact with a mine, the contact would blossom into a bright green pear every time the line swept past its position.
No sooner had the Spadefish dived than Lockwood, elbow-to-elbow with Underwood, heard the sound of a bell, clear and undistorted, tolling from the FM sonar’s speaker—the infamous hell’s bells! The instant the bell began ringing, the sonar technician at the PPI console sang out, “Mine contact!”
Ahead and to the right of the advancing Spadefish danced a dummy mine on a deep-anchored cable.
Triumph! thought Lockwood. The damned thing actually worked! Not only did it locate mines, but with proper handling and a studied touch of its controls it could point a sub toward an open path through them. Even now the Spadefish, advancing submerged at three knots, swept on through the minefield, “blobs glowing on the sonar screen not so much like pears but like big juicy lightning bugs.”3 Lockwood was ecstatic. He’d put his reputation on the line to prove that FM sonar would work. And it did. As he slapped a still skeptical Underwood on the back, he saw with his own eyes that it was the secret weapon he’d dreamed of that would get his subs back into the Sea of Japan to finish off the Japanese.
Sure, FM sonar was only as good as the men who operated it. Both the operators and the captains of the sonar-equipped subs would need specialized training on the equipment, not just to learn how to take full advantage of its abilities and to overcome its limitations, but also to gain confidence that its employment against enemy minefields would open new horizons for the sub force. Until that moment off Oahu, when hell’s bells and big, juicy lightning bugs announced the presence of mines, Lockwood, like every submariner, had accepted the fact that mines embodied an occupational hazard and that nothing could be done about it. Now, FM sonar would change everything. As operators gained experience and as the sonar underwent improvements, submariners could then embark in a great fleet of FM sonar-equipped submarines with little to fear from the great mine menace. Then and there Lockwood vowed that he would see to it personally that both captains and sonar operators received the training they would need on FM sonar before setting out on patrols.
To realize this goal, Lockwood would have to negotiate bureaucratic roadblocks and manufacturing bottlenecks. He also faced another serious problem over which he had no control. Though a prototype unit from UCDWR’s labs had found its way aboard the Spadefish, future production units were destined not for the sub force but the Navy’s minesweeper force. This despite the fact that the mine force had flatly rejected the units because their poor performance made minesweeping more dangerous than it already was using traditional methods of paravanes and cable cutters.
Fuming that the needs of the sub force had been ignored, Lockwood presented his argument directly to Admiral Nimitz for the acquisition of the unwanted minesweeper FM sonar units for submarine use. Meeting with the fleet admiral in mid-July, Lockwood made a presentation that included details of the tests conducted in San Diego and off Oahu in the Spadefish. While he was at it he made a pitch for getting his hands on as many sets as he could to equip submarines undergoing overhaul on the West Coast and, if possible, some of those based in Pearl. As Lockwood talked and talked, Nimitz, his pale blue eyes assessing Lockwood’s effervescent enthusiasm for his pet project, listened carefully. Lockwood completed his presentation with, “Eventually, Admiral, with this new sonar, we’ll crack the Sea of Japan without losing a ship or man to the minefields.”4
Nimitz was a realist. Though he shared Lockwood’s enthusiasm for such a mission and appreciated that ComSubPac was not a man to unnecessarily risk men’s lives on harebrained schemes, he may have had doubts that a force of submarines equipped with Lockwood’s magic gear could run the gauntlet without incurring losses. He may have even thought that Lockwood’s chances of twisting arms at the Navy Department, which would have the final say on the diversion of sonar sets, were slim to none, and that nothing more would come of the mission. Nimitz, weighing the risks and potential rewards in Lockwood’s proposal, gave it his approval. Even with Nimitz’s approval in hand, Lockwood faced a tough battle. He would have to convince the Navy’s bureaucracy in Washington that if his submarines were equipped with the FM sonar units destined for minesweepers, they would become one of the keys to ending the war in the Pacific sooner rather than later. To win that battle Lockwood would have to enlist the Navy’s top admiral, CNO Ernest King, to his cause. The problem with this line of attack was that King in Washington and Lockwood in Pearl Harbor were based almost five thousand miles apart. A letter to King outlining the problem was impractical, and a lengthy telephone conversation over already jammed phone lines to the States meant solely for priority communications wasn’t possible. How to get himself in front of King, even for a few minutes? Lockwood pondered this problem for a time until a solution presented itself via a secret communication to all commands in Hawaii: A top-level strategy meeting between President Roosevelt, General Douglas MacArthur, Admiral King, and Admiral Nimitz would take place in Honolulu in late July.5 Lockwood saw his opportunity and seized it.
Admiral King arrived in Pearl Harbor days ahead of President Roosevelt, who had embarked from the States aboard the heavy cruiser USS Baltimore (CA-68). Fresh from a tour conducted by Lockwood of a submarine about to sail on a war patrol, King agreed to sit down with Nimitz and Lockwood to discuss the FM sonar issue. Strange as it seems, King did not tour the Spadefish preparing to depart on her first war patrol from Pearl Harbor on July 23. The reason might be that her follow-up trials had not been as successful as the first one Lockwood had witnessed and that he didn’t want to reveal that fact to King or Nimitz. As it turned out the Spadefish sailed with her FM sonar unit out of commission.
King quickly grasped the importance of Lockwood’s proposal. He, like Nimitz, believed submarines could play a decisive role in the final collapse of Japan—they’d already brought Japan to the brink—and so he was eager to make it happen. The CNO, with a glance at a smiling Nimitz, nodded his assent to Lockwood’s plan. Now all it would take to start untangling the red tape that had bound the FM sonar sets over to the mine force and divert them to ComSubPac’s use would be a few words from King to his chief of plans. Little wonder that Lockwood felt he’d successfully moved heaven and earth to get what he needed to begin serious planning for a raid into the Sea of Japan. All he needed to make
that happen were more submarines and more FM sonar sets. And one more thing, too: He needed submariners to buy into his plan.
CHAPTER SIX
Wolf Pack
Fresh from a two-week stay at the camps outside Fremantle set aside for the rest and recuperation of submariners, the Bonefish’s crewf reported aboard their ship, which had been refitted by the submarine repair unit of the tender USS Griffin (AS-13).
On September 5, 1944, the Bonefish, setting out on her sixth war patrol, stopped at the forward supply base established at Port Darwin on the north coast of Australia to top off with food and fuel. In addition to his orders governing the Bonefish’s patrol, Edge had orders to operate with the submarines Flasher (SS-249) and Lapon (that veteran of an earlier patrol in the Sea of Japan) as part of a coordinated attack group, in other words, a wolf pack. The pack’s operating area encompassed the waters of the Sibuyan Sea south of Luzon, Philippines, and the South China Sea west of Luzon.
The German Ubootwaffe had successfully employed U-boat wolf packs against Allied convoys in the North Atlantic. These wolf packs had come perilously close to severing the only supply lifeline England had. It wasn’t until the spring of 1943 that the Allies, after breaking the German Enigma submarine codes, began sinking hundreds of U-boats, thus saving England from almost certain defeat by Nazi Germany.