Night Fight at Kula Gulf

The fierce surface actions of the 1942 Guadalcanal campaign highlighted Japanese excellence in night fighting, at heavy cost to the U.S. Navy. But by March 1943, it seemed that the Americans had finally taken the measure of the Japanese, when Rear Admiral Aaron S. Merrill’s task group of cruisers and destroyers ambushed and sank two Japanese destroyers in Kula Gulf.

American radar had proven superior to Japanese night optics, allowing gun power to sink the destroyers before they could respond. The sinking of a U.S. Navy destroyer at the same location four months later might nevertheless have sounded a warning note, as a torpedo from the destroyer Niizuki ran 20,000 yards to blast the USS Strong (DD-467) in another encounter early on 5 July. But the Americans ascribed that sinking to a midget submarine rather than the Japanese ship, which seemed impossibly far away to land such a blow.

When Rear Admiral Walden L. Ainsworth settled on his battle doctrine, he had the March engagement far more in mind than the more recent sinking of the Strong. If his cruiser-destroyer force met Japanese light forces at night, it would use search radar first to detect the Japanese and then use radar-directed guns to smash their ships before they could even attempt a torpedo riposte. Ainsworth’s force was built around three big cruisers—the USS Honolulu (CL-48), Helena (CL-50), and St. Louis (CL-49)—with a total of 45 6-inch guns, surely more than enough gun power to devastate any Japanese destroyers they met.

Intercepting a Japanese Supply Run

Ainsworth developed two night battle plans. In the first, he would engage the enemy at a range of between 8,000 and 10,000 yards, well within the effective range of his radars and beyond visual sighting distances. In the second, tailored for higher visibility, he would engage at longer ranges and use starshells to supplement his radars.

Ainsworth got the opportunity to put his battle plans into effect when, on the afternoon of 5 July, he got word of a possible Japanese supply mission into Kula Gulf. As his force was then heading back down “the Slot” (New Georgia Sound), he came about and raced to intercept. The word was, in this case, correct. Rear Admiral Teruo Akiyama was heading into Kula Gulf with six destroyers and four destroyer transports.

Akiyama’s plan called for seven of his ships to steam south into the gulf to land troops and supplies. These would proceed in two groups: the First Transport Group, with one destroyer and two destroyer-transports, and the Second Transport Group, with two destroyers and the remaining two destroyer transports. Akiyama, with the Niizuki, Suzukaze, and Tanikaze (the Support Group), would loiter at the northern entrance of the gulf to protect the other ships.

The night was a close one, with visibility estimated by the Americans to be between 2,000 and 6,000 yards—ideal for Ainsworth’s planned radar-directed gunfire tactics. And things seemed to go to plan when Akiyama’s ships appeared on the flagship Honolulu’s SG radar screens. The cruiser’s radar plot logged the contact at 0136.5, reporting ships bearing 210 degrees and 26,500 yards away. Within five minutes, the plotting team reported that the contact consisted of three or four ships heading out of the gulf on a course of 355 degrees at 21 knots. Although the Japanese force was yet too far to engage effectively, the clock had begun to run and would now run remorselessly.

Which Group to Target?

At 0141, Ainsworth ordered his four destroyers to leave their screening positions and assume stations ahead and astern of his cruisers. A minute later came an order for all ships to turn 60 degrees left to close with the enemy. Not yet having assumed their new stations, the destroyers struggled to comply with both maneuver orders. Then, three minutes after the order to turn, the Honolulu’s SG radar operators saw the pips on their radar screen start to separate.

The radar operators were seeing the Second Transport Group, which had been traveling with the Support Group, turning to head south into the gulf. As the transport group separated from the Support Group, the Honolulu’s combat information center team evaluated the latter as containing three to five ships and the former as including three to four larger ships.

Which group to engage? First, Ainsworth had to bring his force back into the line-ahead formation from which he intended to fight. An order went out at 0149 for all ships to turn right 60 degrees, putting them back on their original base course of 292 degrees, still closing Akiyama’s group, but more slowly. Again, the destroyers struggled to comply. A minute later, the admiral ordered the cruisers to set up on the northern group as their target.

And then he hesitated. Perhaps the southern force, with its apparently larger ships, should be the cruisers’ target instead. Ainsworth first tried to coach his destroyers onto the northern force and his cruisers onto the “heavier ships.” Then, at 0154, “Hold everything for a minute” went out over TBS (the tactical voice radio net) as the admiral tried to make sense of the situation.

His hesitation lasted only a minute, as shifting to the 15,000-yard short scale of the SG radar revealed that the two target groups were 8,000 yards apart and separating rapidly. At 0155 Ainsworth concluded the distance separating the groups was too great to target both and so reaffirmed that the Support Group would be the target for all ships.

Two minutes later, after their fire control teams struggled to discern their targets from the blurred pips of Akiyama’s formation, the three cruisers reported their readiness to fire. Their guns thundered into action shortly after 0157, with the Honolulu’s gunnery officer noting a range of 6,650 yards to the target. Ainsworth had come closer to the Japanese formation than he intended, but did he come too close? No ship in his force reported visual contact with the enemy, even with radar to guide them. Surely no Japanese ship could have sighted his force.

The battle appeared to be won in the first five minutes. Ainsworth’s three cruisers fired more than 1,500 6-inch shells in that time, with most targeting the Niizuki. The big destroyer’s plight was hopeless as round after round slammed into her. She drifted out of the fight on fire, surrounded by 6-inch shell splashes, with her communications and steering gear wrecked.

Nor were the Suzukaze or Tanikaze spared, with a gun damaged, a searchlight destroyed, and an ammunition locker ignited in the former and the latter hit by a single round that, luckily for her, was a dud. The fire control teams of the cruisers shifted fire as radar operators reported targets disappearing from scopes and the gun director personnel saw them burst into flames. As the cruisers ran through their stocks of flashless powder, the muzzle flashes of their guns continuously lit up the night.

A Surprising Reversal of Fortune

Sure that Akiyama’s formation had been completely destroyed, Ainsworth ordered his ships to reverse course to starboard and steam back toward the Supply Group seen entering the gulf.

The turn had just been ordered at 0203 when a torpedo blew off the Helena’s bow behind her forward 6-inch turret. More hits followed at 0205 and 0206, breaking the cruiser’s back and wrecking her steam plant. Doomed, she sank 20 minutes later. Shortly after the last torpedo hit the Helena, a fourth connected with the St. Louis. Fortunately for the cruiser, this one did not explode.

How was this possible? Ainsworth was sure that he had taken Akiyama’s formation by complete surprise and had annihilated it before it could launch any effective counterstroke. And even if the Japanese had somehow managed a Parthian shot from amid the shell splashes, their torpedoes arrived more quickly than the admiral thought possible.

The answer was threefold: well-trained crews, excellent optics, and powerful torpedoes. Akiyama was taking the Support Group and the Second Transport Group south into the gulf when the Niizuki’s radar showed a contact 5,500 yards to the northeast. This was a phantom, as Task Group 36.1 was still miles away, but it prompted Akiyama to turn both groups north and so put him on a collision course with Ainsworth.

Superb night optics and alert lookouts then took a turn. The Imperial Japanese Navy stressed night fighting, and its destroyers carried enormous pedestal-mounted binoculars optimized for night vision. At 0147, the Niizuki’s lookouts reported they had glimpsed shadows 7,700 yards to the northeast. The actual range to Ainsworth’s formation was more than 14,000 yards, making the sighting a remarkable feat on a night when no U.S. commander estimated the visual sighting range to be more than 6,000 yards.

Akiyama took no immediate action based on this uncertain report. He had detached the transport group southward at 0144 and made no immediate move to recall it. However, continuing reports of ships to the northeast at decreasing ranges prompted the admiral to order the Support Group to speed up to 30 knots and turn 40 degrees to port at 0152, opening their torpedo launching arcs against a possible force steaming on an west-north-west course abaft their beam. Akiyama’s timing was excellent, as Ainsworth’s force had turned to that course just two minutes before the Japanese admiral’s order. By 0156, the reports had become solid enough for Akiyama to have his destroyers launch their torpedoes. This he ordered at 0157, just as Ainsworth’s ships were opening fire. Lookouts and night optics had done their jobs; now it was the turn of torpedoes and torpedomen.

Superiority of the Japanese 93s

The Niizuki, hit hardest and first, may never have gotten her fish in the water, but the Suzukaze and Tanikaze each emptied her eight torpedo tubes before turning away from the U.S. formation and into a smoke screen. The torpedoes in this case were formidable oxygen-fueled Type 93s, which could run much faster for much farther than the Mk-14 torpedoes carried by Ainsworth’s destroyers. The Suzukaze had swung left to unmask her torpedo battery and began to launch her Type 93s at 0158. The Tanikaze followed a minute or two later, after waiting for the Suzukaze to clear her line of fire. The Suzukaze’s torpedoes made the first hit on the Helena. The Tanikaze scored three hits for eight shots (two on the Helena and the dud that struck the St. Louis).

The torpedo strikes were much discussed in the after-action analyses of the battle. The gunnery control officer in the Honolulu calculated the torpedoes must have run 8,500 yards at a speed of 36.5 knots—a performance slightly superior to the U.S. Mk-14. Ainsworth speculated that they might have come from a destroyer closing to within 4,000 yards of the task group and launching at 0200, yielding a performance similar to the American torpedo.

But other facts argued against this. Of the seven ships in Task Group 36.1, only two had reported seeing a destroyer maneuver in this way. Moreover, Ainsworth estimated that the enemy ship would have had to start her charge before 0154 to get to the firing position—contrary to his belief that he had surprised Akiyama. A submarine was another possibility (and had been used in the past to explain otherwise inexplicable torpedoings), although the admiral could not point to a submarine sighting during the night.

What-Ifs and Dangerous Assumptions

A study published in October 1943—part of a series recording and commenting on U.S. Navy battle experiences—looked at the issue in detail. It acknowledged the charging destroyer theory and accepted the idea that a destroyer could have started a charge before Ainsworth’s cruisers opened fire. The author of the study noted that the hits taken by the Helena would not have “required an extraordinary type of torpedo” if the torpedoes had been launched between 0151 and 0154.

As to that, the study concluded that TG 36.1 likely was detected before it opened fire, probably by radio direction-finding exploiting “the volume of TBS traffic in [the] Task Group” and visual tracking. While the study was right to credit Akiyama’s force with seeing TG 36.1 before being attacked, it was of course wrong to focus on radio direction-finding and quite wrong to reject the possibility of superior Japanese torpedoes. The U.S. Navy would not fully appreciate the capabilities of the Type 93 torpedo until early 1944.

Could Admiral Ainsworth have avoided the sinking of the Helena? What-ifs are perilous, but they can illuminate history as it happened. In the end, the Helena’s fate came down to a matter of time—that most precious of things in a night battle. Despite having contacted the Japanese well outside even their visual sighting range, time slipped through Ainsworth’s fingers. Once he turned toward the radar contact, his force was closing the Support Group at a rate of more than 1,000 yards per minute. A turn at 0148 (rather than 0150) would have given him the battle range he was seeking.

Even opening fire promptly after the turn would have yielded an initial engagement range of a bit more than 9,000 yards. This would have started the battle two minutes before Admiral Akiyama began to respond to his lookouts’ sighting reports. And if Ainsworth had adopted his plan to engage with starshell support at still longer ranges, the Japanese force would have had even less advance notice of the American attack.

Of course, none of this would have guaranteed the Helena’s survival. Even taken by complete surprise, the Suzukaze and Tanikaze still might have unleashed devastating torpedo broadsides. The Niizuki might have joined them with four torpedoes of her own, had the U.S. cruisers’ gunfire been less effective. But both reaction time and ranges would have been longer, the former giving American gunfire more time to take effect and the latter decreasing the chances of hits if torpedoes were launched. Admiral William F. “Bull” Halsey Jr., in his endorsement to Ainsworth’s battle report, opined that well-controlled radar-controlled 6-inch gunfire would be devastating even at ranges beyond 12,000 yards. As Halsey put it: “Every effort must be bent towards maximizing the present tremendous superiority of our gun-fire, and minimizing the danger from enemy torpedo fire.” That is, it was better to engage at longer ranges to minimize the torpedo threat. In that view, Pacific Fleet Commander-in-Chief Admiral Chester W. Nimitz fully concurred.

But even when writing a response to the battle experience report in March 1944, Ainsworth was adamant that he had taken Akiyama’s force “completely by surprise.” Ainsworth assumed he had time on his side—that he could surprise the Japanese as long as he relied on radar and kept out of visual contact. This proved a dangerous assumption to make.

There was more of the Battle of Kula Gulf to be fought, as the Second Transport Group steamed north to enter the fray, and another night battle for Ainsworth to fight a week later—but those are stories for another day. 

Times in these accounts have been adjusted based on observed events, with the times given in the Honolulu’s after-action report used as a baseline.