Through the entire month of September, Japanese transportation runs, made by destroyers, went unopposed by anything but sporadic air attacks from Henderson Field. Responsible for this lack of action was partially the Imperial Navy - submarines had accounted for Wasp, damaged Saratoga and North Carolina, while carrier air units had knocked Enterprise out of the action. With only Hornet remaining, supported by Washington, the U.S. Navy and especially Vice-Admiral Ghormley were reluctant to risk operating without a major reason. 
    Frequently, destroyer-transports visited the beleagured Marine garrison leaving supplies, but there were voices that feared a lack of reinforcements would invite disaster. Army General Harmon, for example, advocated the abandonment of the operation to capture Ndeni in the Santa Cruz islands in favor of reinforcing Guadalcanal. 

    Meanwhile, Admiral Ghormley could not simply drop Ndeni - too often was he questioned about the matter by Admirals Nimitz and King. However, he gave in to Harmon's persuasion. Army units would be send to Ndeni (which subsequently turned out a misinvestment); a further Marine regiment would deploy to Guadalcanal. 
The transports McCawley and Zeilin were loaded and send to Guadalcanal under the direct protection of three destroyers and three destroyer-minelayers, with task forces centered on Hornet and Washington respectively in support and TF 64 under Rear-Admiral Norman C. Scott providing screening to the west, with orders to engage in night battle if possible. 

    In the meantime, the IJN had not been lazy. Destroyers had brought in a large part of General Hyakutake's 17th Army. 22.000 men had been landed by several large runs of the Tokyo Express, and besides these already major reinforcements, the Shortlands, Japan's main destroyer base these days, was filled with further reinforcements including heavy artillery pieces. For this special run, the IJN had brought along a special novelty to this area, the fast seaplane tenders Chitose and Nisshin, which had had several dubious roles in the last few months (including carrying midget submarines to Midway for use in the supposed decisive battle) and could add this mission to a large résumé under the subject of special assignments. 

    Six destroyers would cover the mission, to which, seing its importance, Vice-Admiral Mikawa Gunichi added a further measure of security. Having seen the last Express runs hit by SBDs and fighters from Henderson Field, Mikawa was certain that something needed to be done to cover the slower-than-usual run that night. He added what was left of Rear-Admiral Goto Aritomo's Cruiser Division Six into the action with the mission of bombarding Henderson Field and reduce its air component to impotence. Goto sported only three heavy cruisers after the loss of Kako off Kavieng during the aftermath of the Battle of Savo Island, but his left-over force, Aoba, Furutaka and Kinugasa still carried eighteen 203mm guns. Mikawa added two destroyers to screen this force as it went in harm's way, hardly enough for anti-submarine or anti-air work, but obviously all Mikawa had. 

    From Espiritou Santo, the transport force under Rear-Admiral Turner set sail on the 9th of October, heading north by west. All covering groups had been on sea by that time, but both Washington's and Hornet's groups were far off and would not be risked unless heavy enemy ships were sighted. It was left to Rear-Admiral Norman Scott's TF 64 to counter any minor threat, and especially any Tokyo Express, that the Japanese might send south. 
Scott remained in the vicinity of Rennell Island with his four cruiser, five destroyer force, awaiting notice of incoming enemy forces he could intercept. Scott had been on station for two days when, on October 11th, he was notified that a large Tokyo Express was supposed to come down the Slot during the night. He set course for Savo Island, which he would have in sight by 2300. 

    While Scott made his way undetected and unexpected north, both Admiral Goto and Rear-Admiral Joshima Takaji, commanding the seaplane carrier group, sped south-eastward totally oblivious of the danger they were facing. Joshima was ahead of Goto, who trailed with his formation forming a T: his destroyers flanking his flagship Aoba, with Furutaka and Kinugasa in line behind his flagship. 

    Scott had headed almost directly north until he was the same latitude as Cape Esperance, the western tip of Guadalcanal, then shifted his course north-east to cover the entrances to Iron Bottom Sound. His force was deployed in a simple line ahead lead by the destroyers Farenholt, Duncan and Laffey, followed by Scott's SC-radared flagship San Francisco, SG-radared light cruiser Boise, SC-radared heavy cruiser Salt Lake City, and SG-radared light cruiser Helena. Trailing these cruisers were destroyers Buchanan and McCalla. Scott's decision on what ship to employ as flagship was obviously unlucky, for his SC radar was of markedly lower performance than the SG version, and besides, faulty intelligence on Japanese radar receivers precluded the SC radar's use. 

    Scott was intend on hitting Joshima's reinforcement convoy, wrongly reported as containing two cruisers instead of the two seaplane carriers, and according to his battleplan, the dangerous seaplanes his own cruisers carried (a steady fire hazard, as South Dakota would prove during the Second Naval Battle of Guadalcanal) were flown off to Tulagi saving only one plane per ship. 

    As it happened, it was those planes that had flown to Tulagi, employed as night reconnaisance units, which spotted Joshima's force at 2250 off Tassafaronga, where the force had been busily offloading its cargo for the previous fifty minutes. Admiral Scott, who had not expected Joshima to slip past him, shifted his course slightly but did not enter the sound, awainting amplification. At 2333, he ordered a column turn to the left to reverse his course. By 2323, Helena's powerful SG radar had made contact with Goto's force, but the information did not reach Scott. 

    The turn didn't turn out as thought. San Francisco, Scott's flagship, turned simultaneously with the three leading destroyers, and the rest of the column followed Scott. This brought Captain Robert G. Tobin, in Farenholt and originally leading the formation, out of the same and on the northern flank. 

    By the time the fleet had concluded its turn, Boise, Helena, Salt Lake City and at least Duncan held contact with Goto, and Boise finally informed Admiral Scott by announcing bogies bearing 65 degrees. This caused considerable confusion, again delaying the general open fire, since Boise failed to amplify whether she meant 65° relative (i.e. sixty-five degrees off to the right of her own heading, which would have been roughly to the east-north-east) or true (i.e., sixty-five degrees on a compass -- dead aft of the formation). It turned out that Boise meant relative, but that information came to late to be of much use as the following minutes would show: Duncan, center ship of the van destroyers, had already had enough and, having the enemy on her fire-control radar, she charged the enemy to deliver a torpedo attack. 

    While Duncan charged, San Francisco finally acquired a target, but not knowing the identity, held fire. Tobin's destroyers were still an unknown factor as far as their position was concerned.  

    A mere 5000 yards distant Goto's ships were moving directly into the center of the American line, which Goto, deeply feeling that no American was present, considered to  be Joshima's reinforcement group. It was up to Helena to teach him otherwise. Captain Hoover was certain he had the enemy before him and queried Scott to open fire. Scott replied, "Roger", which he intended as a confirmation of receipt, but if unqualified it meant open fire as well, and Hoover interpreted it as such. He switched on his searchlights, aiming them on Hatsuyuki, the left-wing destroyer, and opened fire with his fifteen 155mm guns at 2346. 
That action caught Scott off-guard, but he did not prevent the rest of his line from opening fire on the enemy. Duncan, now only a few hundred yards from Kinugasa, joined in, but was quickly disabled. 

     Only a minute later, Scott ordered a cease fire to sort out targets (still concerned about Tobin and his destroyers, which were indeed badly positioned), but no every ship complied. Farenholt got hit twice by 155mm shells from U.S. cruisers, but survived. And having established that Tobin was out of the way, the American line once more opened up in full. 

    Goto, too, had been surprised, but for several minutes his flagship had flashed the recognition signal in a vain attempt to get "Joshima" to reply. Goto now knew who was before him, but he would not be able to appreciate his mistake for long. A salvo from Boise smashed into Aoba's bridge and mortally wounded the Admiral. 

   Aoba was soon blazing from numerous hits and staggered north behind a smoke cordon. Furutaka, in her wake, gallantly interposed herself between Aoba and the enemy, and paid the price in becoming the main target for the U.S. line. She, too, staggered away blazing, but she would not make it. 

   Kinugasa had turned north without waiting for orders on seeing the arc of guns before her and moved away to the north, adding long-range fire to aid her comrades. She shot excellently - shells struck Boise in the forward 155mm magazine, which fortunately did not explode. 
Coming up from behind Boise, Salt Lake City interposed herself between the two battling cruisers, firing on Kinugasa and receiving fire in return for medium damage and low casualties. 
    In the meantime, fire from San Francisco and despatched the destroyer Fubuki, and all that was still swimming on the IJN side retired northward at best speed. Scott gave chase for a few miles, but at 0200, he broke off and retired. Furutaka and Fubuki had been sunk; Aoba, Kinugasa and Hatsuyuki were retiring with different degrees of damage. 

    On the U.S. side, Duncan sank during the day, and Boise and Salt Lake City were ordered home for repairs. Scott had won a victory, but by a slight margin only, and he had not prevented the resupply and reinforcement effort. A strategic draw (one mission prevented, one not) was the result, and intensified operations followed.