Operation Landcrab

This was the US recapture of Attu island in the Aleutian islands group off Alaska in an operation often called 'Sandcrab' (11/29 May 1943).

Attu island lies near the western end of the Aleutian islands chain, some 740 miles (1190 km) to the west of Dutch Harbor on Unalaska island at the chain’s eastern end, and just 650 miles (1045 km) from Paramushiro in the Japanese-controlled Kurile islands group. Attu is about 38 miles (61 km) long and 14 miles (22.5 km) wide with an area of 344.7 sq miles (893 km²), and like most of the Aleutian islands is mountainous and barren, with a maximum height of 2,946 ft (898 m) toward its western end. The few beaches are narrow and steep, and there are numerous offshore rocks and strong currents. There are, however, some small protected anchorages at Holtz Bay and Chichagof Harbor on the north-east coast, and Massacre Bay on the south-east coast.

The islands of Attu and Kiska, at the western end of the Aleutians, had been taken by the Japanese on 3/7 June 1942 in the ‘Aq’ and ‘Aob’ sub-elements of ‘Al’ undertaken in parallel with ‘Mi’ (ii) against Midway, and within days the US Joint Chiefs-of-Staff had agreed that the sooner the recapture of the islands was attempted, the less the effort which would be required. The Joint Chiefs-of-Staff thought that the Japanese attack on the Aleutians and the occupation of its westernmost islands might be part of a holding action designed to screen a Japanese offensive to the north against the USSR’s eastern extremities, namely Siberia’s maritime provinces and the Kamchatka peninsula.

As a result, the Joint Chiefs-of-Staff informed Rear Admiral Robert A. Theobald and Major General Simon B. Buckner, commanding Task Force 8 and the Alaska Defense Command respectively, of their concerns and the possibility of a Japanese occupation of St Lawrence island in the Bering Sea and of nearby Nome and its adjacent airfields on the Alaskan mainland. Supporting the possibility of an invasion of the Alaskan mainland were reports of a Japanese fleet operating in the Bering Sea. On 20 June alone, there were three separate sightings of a Japanese fleet somewhere between the Pribilof and St Lawrence islands, suggesting that the Japanese were about to raid or invade the Alaskan mainland, with Nome the likely objective. As a result, there emerged a sense of extreme urgency, leading to the first mass airlift in US history as, within 36 hours, military as well as commandeered civilian aircraft flew nearly 2,300 troops, artillery and supplies, to Nome.

Not until a time early in July, when US intelligence reported with some certainty the departure of Vice Admiral Boshiro Hosogaya’s 5th Fleet from the Bering Sea, did the perceived threat of invasion of the Alaskan mainland decline, allowing for the redeployment of many of the troops hastily assembled at Nome.

In keeping with the desire of the Joint Chiefs-of-Staff for a rapid move to retake Kiska and Attu islands, Theobald and Buckner agreed to establish a series of airfields to the west of Umnak island, about two-thirds of the way from the eastern end of the Aleutian islands chain, from which bombers could launch attacks against Kiska, the closest of the Japanese-held islands.

The first of the Aleutian islands group to be reoccupied was Adak, some 400 miles (645 km) from Umnak. On 28 August 1942, 38 men of the Alaska Scouts unit landed on Adak and established that while the Japanese had visited the island they had established no permanent garrison there. Two days later, a force of 4,500 men (4th Infantry and 807th Aviation Engineer Battalion) landed on the island and then, in a struggle against weather and terrain, the engineers drained a small lagoon and turned it into a usable airfield in just 10 days. On 14 September Consolidated B-24 Liberator heavy bombers took off from Adak to attack Kiska, some 200 miles (320 km) distant.

On 12 January 1943 a force of 2,100 men under the command of Brigadier General Lloyd E. Jones occupied Amchitka and began construction of an airfield, and the first fighters arrived on 28 January.

Repeated bombings of Kiska during the summer and into the autumn convinced the Japanese that the Americans intended to recapture the island. As a result, by November they had increased their garrisons on Kiska and Attu to 2,900 and 1,000 men respectively. During the winter months the Japanese counted on the shortness of the days and the general adversity of the weather to protect them from any serious attack.

Although continually hampered by the very considerably greater priority accorded to the campaigns in the Solomon islands group and New Guinea, the build-up of the US Army’s Alaska Defense Command continued, reaching 94,000 men by January 1943, the time by which 13 more bases had been built in Alaska, many of them in the Aleutian islands group. With an unopposed US Army landing on Amchitka island on 11 January, troops of the Alaska Defense Command were now within 50 miles (80 km) of Kiska. For nearly two weeks, a blizzard prevented all but survival tasks, but then a Japanese reconnaissance aeroplane from Kiska discovered the US beach-head on Amchitka. Harassed by bombing and strafing attacks from Kiska, US engineers continued work on an airfield on Amchitka, completing it in mid-February. Japanese attacks on the island then sharply declined.

As the US forces approached Kiska and Attu islands, the Japanese outposts became increasingly more difficult to resupply. In mid-March, Rear Admiral Thomas C. Kinkaid, who had replaced Theobald in January, established a naval blockade around the islands, and the warships of this blockade force sank or drove off of several Japanese supply vessels, starting on 20 February with the interception and sinking of the 3,130-ton Akagane Maru. The vessel was bound for Attu with troops, munitions and supplies when she was engaged by the heavy cruiser Indianapolis and destroyers Coghlan and Gillespie. A salvo from the heavy cruiser’s 8-in (203-mm) main armament set the Japanese transport vessel ablaze from stem to stern, and she soon exploded. All 140 members of her crew were lost. The passage of the first Japanese convoy, from 9 March, was successful, but the second, which departed Paramushiro on 23 March was not: on 26 March, as this Japanese force, led by Hosogaya, attempted to run the blockade with three transport vessels (Asaka Maru, Sakito Maru and Sanko Maru), escorted by two heavy cruisers, two light cruisers and five destroyers, the largest naval engagement of the Aleutian islands campaign took place as the Battle of the Komandorski Islands on 27 March.

When the USA learned that the Japanese planned to send a supply and reinforcement convoy to their forces on the Aleutian islands group, a task force under the command of Rear Admiral Charles H. McMorris was despatched to intercept this with Task Group 16.6 comprising the heavy cruiser Salt Lake City, light cruiser Richmond and destroyers Coghlan, Bailey, Dale and Monaghan.

The US intelligence estimate was that the Japanese escort comprised one heavy cruiser, one light cruiser, and four destroyers, but Hosogaya’s 5th Fleet had been reinforced by two more cruisers, so that the Japanese Northern Force actually comprised heavy cruisers Nachi and Maya, light cruisers Tama and Abukuma, and destroyers Wakaba, Hatsushimo, Ikazuchi, Inazuma and Usugumo, of which the last did not become involved as she was escorting Sanko Maru.

Early in the morning of 26 March, the Japanese convoy was intercepted by the US picket line some 100 miles (160 km) to the south of the Komandorski islands group, which are a westward extension of the Aleutian islands group but owned by the USSR, and 180 miles (290 km) to the west of Kiska island, just to the west of the international date line. As a result of the battle’s remote location and its nature as a chance encounter in the open ocean, neither fleet possessed either air or submarine assistance, making this one of the few engagements fought entirely between surface ships in the Pacific theatre, and at the same time one of the last pure gunnery duels between fleets in naval history.

Although the Japanese cruisers considerably outgunned the US force, the engagement was tactically inconclusive. The two sides exchanged fire for a period exceeding four hours. Nachi was hit a number of times, but Salt Lake City was disabled by shock damage from her own gunfire and a hit in her after engine room. Poor damage control resulted in a complete loss of power, and McMorris ordered his destroyers to execute a desperate torpedo attack. At this point the Japanese suddenly broke off and fled. Hosogaya later explained that he was short of ammunition and fuel, and a number of near misses from the US ships were mistaken for aircraft bombs, leading the Japanese commander to believe he was under air attack. Hosogaya was subsequently forced into retirement.

Both forces had suffered damage, the US warships escaping almost by luck. As indicated above, and with his force on the edge of victory, Hosogaya failed to appreciate the significant damage his ships had inflicted and, fearing the arrival of US warplanes, retired without destroying his enemy. This amounted to a strategic defeat, as it ended Japanese attempts to resupply the Aleutian isoand garrisons by surface ship, leaving only submarines to conduct supply runs. Hosogaya was accordingly retired from active service after the battle.

Thus a smaller US Navy force compelled Hosogaya to retire without completing his mission, and as a result the garrisons at Attu and Kiska islands could rely only on the altogether smaller quantities of supplies which could be delivered by submarine.

The US losses had been once heavy cruiser severely damaged and two destroyers slightly damaged, together with seven men killed and 20 wounded, while those of the Japanese had been one heavy cruiser moderately damaged and one heavy cruiser slightly damaged, together with 14 men killed and 26 wounded.

Of the two islands held by the Japanese, Kiska was the more important in purely military terms. Containing the only operational airfield and possessing the better harbour, Kiska was therefore scheduled for recapture before Attu. For that purpose, Kinkaid asked for a reinforced infantry division, giving him 25,000 troops. When not enough shipping could be made available for the support of so large a force, Kinkaid urged that Attu be substituted for Kiska as the objective, indicating that Attu was defended by no more than 500 men, whereas Kiska was thought to be held by 9,000 men, and the task would therefore demand no more than one regiment. Kinkaid also noted that US forces based on Attu would be astride the Japanese line of communications and thus in a position to cut off Kiska from reinforcement and supply, which in time would cause Kiska to ‘wither on the vine’.

After Joint Chiefs-of-Staff approval had been gained on 1 April for the ‘Landcrab’ operation to retake Attu and the required shipping had been obtained, work began on the detailed plans to recapture the little, fog-shrouded island at the western end of the Aleutian islands chain. Attu is dominated by snow-capped mountains whose slopes fall steeply to treeless valleys carpeted with muskeg, a ‘black muck’ covered with a dense growth of lichen and moss. For much of the time in the outermost part of the Aleutian islands group, the muskeg is barely firm enough for a man to cross on foot. This is the result of the warming effect of the Japanese current, which also creates the area’s thick fogs, pervasive damp and frequent storms.

Commanding the North Pacific Force, Kinkaid pulled together an imposing armada to support the invasion. In addition to an attack force of three battleships, one escort carrier and seven destroyers to escort the landing force and provide it with fire support, Kinkaid had two covering groups comprising several cruisers, destroyers and submarines, for the earliest possible detection of any response by the 5th Fleet, Kinkaid’s Task Force 16 thus controlled Rear Admiral Francis W. Rockwell’s Task Group 51.2 Transport Group with the attack transports Harris, Heywood and Zeilin, transport Perida and high-speed transport Kane, escorted by the destroyers Dewey, Dale, Monaghan and Aylwin, minelayers Sicard and Pruitt, and the TG51.3 Minesweeper Group with Perry, Elliot, Chandler and Long to deliver and land Major General Albert E. Brown’s TG51.4 Landing Force. This last comprised the reinforced 17th Infantry, one battalion of the 32nd Infantry, the 78th Coastal Artillery Battalion in the anti-aircraft role, one battalion of the 50th Engineers and the Scout and Reconnaissance Troop of Brown’s own 7th Division.

Fire support was provided by Rear Admiral Howard F. Kingman’s TG51.1 comprising the battleships Nevada, Pennsylvania and Idaho, escort carrier Nassau with 28 Grumman F4F Wildcat fighters (three in the reconnaissance role) and one Curtiss SOC-3A Seagull in the general-purpose role, destroyer-based seaplane tender Williamson, and destroyers Phelps of Destroyer Squadron 1 and Farragut, Hull, MacDonough, Meade, Edwards, Abner Read and Ammen of Destroyer Division 2.

Cover was provided by Rear Admiral Charles H. McMorris’s TG16.6 Southern Covering Group with the light cruisers Raleigh, Detroit, Richmond and Santa Fe, and destroyers Bancroft, Caldwell, Coghlan, Frazier and Gansevoort, and by Rear Admiral Robert C. Giffen’s force with the heavy cruisers Wichita, San Francisco and Louisville, and destroyers Balch, Hughes, Mustin and Morris.

The submarines Narwhal and Nautilus of the TG16.5 Submarine Group provided navigational and scouting support, the latter with the men of the Provisional Scout Battalion. Other submarines available in the area to intercept any Japanese surface force comprised S-18, S-23, S-28, S-34, S-35 and S-38 of Submarine Division 41 and S-30, S-32, S-33, S-40 and S-41 of Submarine Division 52.

Other elements of TG16 were Rear Admiral John W. Reeves’s TG16.2 Alaska Sector Escort and Supply Force with the destroyer King, high-speed minesweeper Lamberton, light minelayer Ramsay, minesweepers Oriole and Annoy, Canadian corvettes Dawson and Vancouver, gunboat Charleston, ocean tug Tatnuck, fleet tug Ute, netlayers Buckeye and Eucalyptus, four tank landing ships and eight tank landing craft; the TG 6.3 Motor Torpedo Boat Group with the 11 PT-boats of Motor Torpedo Boat Squadron 13; the TG16.8 Attu Reinforcement Group with the transports U. S. Grant, David W. Branch, President Fillmore, Chirikof, Richard M. Rowell, Joseph Henry, Kenneth A. J. Mackenzie and David W. Field carrying the 32nd Infantry less one battalion; the TG16.9 Tanker and Service Group with the oilers Brazos, Cuyama, Platte, Tippecanoe, Guadalupe and Neches, and destroyer tenders Markab and Black Hawk; and Brigadier General John E. Copeland’s TG 16.10 Shemya Occupation Group with the transports St Mihiel, William L. Thompson, North Coast, Alaska and Yukon, and cargo ship Franklin Macveagh carrying the 4th Infantry and 18th Engineers.

Reinforcing the naval support, Major General William O. Butler’s 11th AAF was to provide 54 bombers and 128 fighters for the operation, holding back a third of the bomber force for use against ships of the Japanese fleet. The 11th AAF elements assigned to 'Landcrab' were designated as the TG16.1 Shore-Based Air Group with Task Unit 16.1.1 Air Striking Unit comprising the 28th Composite Group (eight Consolidated B-24 Liberator bombers and 24 North American B-25 Mitchell medium bombers), 404th Bombardment Squadron (eight B-24 bombers), 21st Bombardment Squadron (eight B-24 bombers), 406th Bombardment Squadron (six B-25 bombers), 343rd Fighter Group (50 Lockheed P-38 Lightning heavy fighters and 50 Curtiss P-40 Warhawk fighters), Canadian No. 111 Squadron (16 P-40 fighters) and Canadian No. 14 Squadron (12 P-40 fighters); and the TU16.1.2 Air Search Unit comprising VB-135 at Amchitka (12 Lockheed PV-1 Ventura patrol aircraft), VB-136 at Adak (12 PV-1 aircraft), VP-62 at Adak (10 Consolidated PBY-5A Catalina flying boats) and VP-61 at Amchitka (10 PBY-5A 'boats), and ships in the form of the small seaplane tender Casco, destroyer-based seaplane tenders Gillis and Hulbert, and seaplane tenders Teal and Avocet.

Early in the planning phase, US intelligence upgraded the estimated Japanese strength on Attu from its original figure of 500 men to 1,500 men, prompting a request for additional forces: the island’s garrison, under the command of Colonel Yasuyo Yamasaki, in fact totalled 4,000 men of the 301st Independent Battalion, 303rd Independent Battalion and Chishima Coast Defence Infantry Unit.

Because Buckner had only one infantry regiment in Alaska, widely dispersed throughout the territory, the War Department provided the needed troops from Lieutenant General John L. DeWitt’s Western Defense Command, selecting Major General Albert E. Brown’s 7th Division (17th and 32nd Infantry less the detached 159th Infantry), then stationed near Fort Ord, California, as the formation to recapture Attu. After completing amphibious training during April 1943, the division’s men embarked at San Francisco, reached Fort Randall at Cold Bay on 30 April, and spent the next four days on their transports. As a result of shortages in cold weather equipment, most of the men faced the prospect of combat in normal field gear. Senior commanders realised that the troops would suffer from the weather, but believed that the fight for Attu would be over within three days, especially given the strength of the naval support.

Three weeks earlier, a concentrated air and naval bombardment of Attu and Kiska had begun, but it had then been limited largely to Kiska because of the continual fog covering Attu. Poor weather caused Kinkaid to postpone the departure of the invasion force from Cold Bay to 4 May, a day behind schedule, and as the convoy neared Attu storms and poor visibility forced yet a further delay in the assault until 11 May. The weather also seriously reduced the air and naval attacks against Attu.

Despite unremitting fog, the assault started on 11 May at widely separated points on the eastern portion of the island. In an attack before the break of day, the 7th Scout Company paddled ashore from submarines onto the small Scarlet beach, some 9 miles (14.5 km) to the north-west of Chichagof Harbor, the location of the main Japanese base and Brown’s ultimate objective. Meeting no opposition, the scout company moved inland. At noon, the 7th Division’s reconnaissance troop landed on Scarlet beach and moved to join the scout company. The two units now constituted a provisional battalion, which was to occupy the head of the valley where a pass gave access to one of the valleys leading back from Holtz Bay.

In the meantime, at the end of the western arm of Holtz Bay, the 1/17th Infantry landed on Red beach. It was planned that if this battalion encountered opposition while advancing on Hill X, its first objective, the provisional battalion was to attack the Japanese from the rear. After passing through the rock-studded sea approach to Red beach in landing craft, the 1/17th Infantry had to scale a steep escarpment, which began about 75 yards (70 m) from the water’s edge and rose some 200 to 250 ft (60 to 75 m) above the beach. From there it started working its way along the western side of Holtz Bay virtually unopposed until 18.00, when heavy Japanese fire halted the advance short of Hill X.

While the 1/17th Infantry landed on Red beach, the main attack in Massacre Bay finally got under way as the 2 and 3/17th Infantry landed unopposed on the Blue and Yellow beaches some 6 miles (9.67 km) to the south of Chichagof Harbor. Had the landing not been delayed because of dense fog and high seas, a third battalion combat team (2/32nd Infantry, attached to the 17th Infantry) would also have come ashore. As it was, that unit remained aboard ship until the next day before landing and moving along the same axis as the 3/17th Infantry. Slowed by the slippery muskeg (moss bog), the 2 and 3/17th Infantry stumbled side-by-side up Massacre Valley, dividing on either side of a hogback. Both battalions came under fire at 19.00: part of the way up the ridges overlooking the valley, the Japanese occupied dug-in positions obscured in a thin mist, and were now able pinned down the advancing US infantrymen. Attempts by the 3/17th Infantry, on the left, to reach the regimental objective of Jarmin Pass, at the head of the valley, failed and in the process incurred heavy losses.

A platoon from the 7th Reconnaissance Troop made a subsidiary landing at Alexai Point and joined the main body at Massacre Bay without opposition.

Having already hampered the landings, the fog likewise concealed the attackers from the Japanese. Not until the middle of the afternoon did Yamazaki order his men from their caves to the prepared outer defences surrounding Chichagof Harbor, which extended from Hill X on the western arm of Holtz Bay, southward to Jarmin Pass, and then eastward to Sarana Bay.

When Brown came ashore at Massacre Bay toward the end of 11 May, the tactical situation was far from clear, but the available information did not suggest that a lengthy struggle was imminent. By 21.30, five hours after the start of the main landings, Brown had 3,500 men ashore: 400 at Scarlet beach, 1,100 at Red beach, and 2,000 at Blue and Yellow beaches.

On the northern front, the 1/17th Infantry was close to Hill X and within 24 hours the 1 and 3/32nd Infantry were scheduled to arrive from Adak. In the southern sector, the 2/17th Infantry reported that it was within 1,000 yards (915 m) of the Sarana Pass, and the 3/17th Infantry indicated that it was about 600 yards (550 m) short of the Jarmin Pass.

On the following day the 2/32nd Infantry, aboard ship in Massacre Bay, was to come ashore to reinforce the 17th Infantry. If additional forces were needed, Buckner had agreed to release the 4th Infantry, an Alaskan unit, on Adak island. Everything considered, it would not have been unreasonable to suppose that within a few days Attu would be taken. On the next day, with naval and air support, Brown’s men continued their two-pronged attack toward the Jarmin Pass, but the 17th Infantry’s frontal assaults from Massacre Bay made no ground. As patrols probed the Japanese positions, the 2/32nd Infantry came ashore at Massacre Bay. Meantime, in the northern sector, the 1/17th Infantry, finding the Japanese dug in on Hill X, made a double envelopment which succeeded in gaining a foothold on the crest of the hill, but the Japanese held firm on the reverse slope. That night the first casualty report of the operation revealed that 44 US troops had been killed since the start of the invasion. Further efforts by the Massacre Bay force on 13 May to take the Jarmin Pass again failed, even with the 2/32nd Infantry entering the fight to reinforce the 3/17th Infantry. As US losses continued to mount, front-line positions remained about the same as those gained on the first day of the assault.

Vicious and costly fighting occurred in the north as the Japanese attempted to drive the 1/17th Infantry from Hill X, but the crest remained firmly in US hands at the fall of night. The 3/32nd Infantry had by then landed on Red beach and was moving forward to reinforce the hard-pressed 1/17th Infantry on Hill X.

Naval gunfire and air support of the ground troops continued insofar as the climatic conditions permitted, but the weather as well as the Japanese continued to frustrate the US efforts to advance. Although surface ships bombarded the reported Japanese positions on 14 May, close air support was extremely limited as a result of the incessant fog that engulfed the island. In an attempt to hasten the capture of the Jarmin Pass, Brown ordered a combined attack by his Northern and Southern Landing Forces, each of these having three battalions by this time. While the Southern Landing Force attempted to inch forward up Massacre Valley to gain the pass, the Northern Landing Force was to drive the Japanese off the reverse slope of Hill X, continue to the south and seize Moore Ridge, and then take the Jarmin Pass from the rear. Each attack quickly bogged down. In the northern sector the provisional battalion that had landed on Scarlet beach remained checked, unable to break out to reach the immobile 1/17th Infantry to its east, and when the 3/32nd Infantry failed to reach its assault positions in time, Brown cancelled the combined attack.

That evening Brown’s report to higher headquarters summarised the four days of fighting and ended with the stark assessment that ‘progress through passes will, unless we are extremely lucky, be slow and costly, and will require troops in excess to those now available to my command’. On the next morning success remained elusive until 11.00, when the fog lifted in the northern sector, revealing that the Japanese had pulled back to Moore Ridge in the centre of Holtz Valley, in the process abandoning food and ammunition. The Japanese withdrawal allowed the provisional battalion to break out and eventually to link with the 1/17th and 3/32nd Infantry to the south-east of Hill X. As the men of the Northern Landing Force then entered the valley in pursuit, the relatively clear sky allowed the Japanese troops on Moore Ridge to place accurate fire upon them. Already slowed by that fire, the pursuit ended when a friendly air attack mistakenly hit advancing US troops.

Back on Adak, Kinkaid’s and DeWitt’s forward command post, the situation on Attu appeared grim. Of special concern to Kinkaid was the exposed position of the ships directly supporting Brown’s forces ashore. A Japanese submarine had already made an unsuccessful attack on one of the three battleships, and there were persistent reports that a Japanese fleet would soon arrive to challenge the landing. As a result, Brown was told that the US Navy would withdraw its support ships probably on 16 May but in any event no later than 17 May, leaving him with an unprotected beach-head and a major reduction in supporting fire. Communication problems between Brown and Kinkaid and DeWitt, located more than 400 miles (645 km) distant, coupled with Brown’s continued requests of reinforcements (the latest, on 15 May, for part of Buckner’s 4th Infantry) and a long despatch requesting large quantities of engineer and road-building equipment, and the lack of any positive indications of a speedy breakthrough on Attu persuaded Kinkaid that Brown had bogged down. When he consulted with DeWitt and Buckner, both agreed with him that Brown should be replaced. Upon their recommendation, Kinkaid appointed Major General Eugene M. Landrum to take command of the forces on Attu on 16 May.

An advance by the Northern Landing Force broke the deadlock on Attu on the day Landrum assumed command. By then a foothold on the northern end of Moore Ridge had been won in the centre of Holtz Valley, US forces thereby gaining control of the entire ridge.

Greatly outnumbered by the Americans and in danger of being taken from the rear, the Japanese now pulled back on the night of 16/17 May toward Chichagof Harbor for a final stand. Well before dawn, men of the 3/32nd Infantry in the northern sector moved forward and by daylight discovered that the Japanese had departed. Patrols reported that the eastern arm of Holtz Bay was also free of the Japanese, allowing for much-needed resupply by sea. In the meantime, the 3/17th Infantry in the southern sector, at Massacre Valley, also found previously defended Japanese positions abandoned, and occupied the Jarmin Pass.

The Japanese pullback to Chichagof Harbor followed by the link-up of US forces on 18 May proved to be the turning point of the battle. While nearly another two weeks of hard, costly fighting remained, the uncertainty and frustration of the first few days on Attu never recurred. It was now the slow business of taking the machine gun and mortar nests left on the high ground by the retreating Japanese, but eventually the combined US force, reinforced by the 1/4th Infantry, closed on Chichagof Harbor. The end came on the night of 29/30 May when most surviving Japanese, about 700 to 1,000 men, charged the US lines, screaming, killing and being killed. On the following day the Japanese announced the loss of Attu as US units cleared out surviving pockets.

The Japanese had intended to respond to the US assault on Attu, and concentrated naval force at Ominato, the northernmost port of Honshu island and headquarters of the 5th Fleet, in preparation for a battle in the Aleutians. The planned Japanese naval offensive was then called off, apparently after the fleet carrier Hiyo was torpedoed and damaged by the US submarine Trigger on 8 June, and the battleship Mutsu was destroyed by an accidental magazine explosion at Hashirajima on the same day.

Although mopping-up operations on Attu continued for several days, organised resistance ended with the wild charge of 29 May, and Attu was once more in US hands. The Americans reported finding 2,351 Japanese dead on the island, and it is assumed that another few hundred were buried in the hills by the Japanese. Of an original force of some 2,900 men, only 28 Japanese enlisted men surrendered. Of a US force totalling more than 15,000 men, 549 men had been killed, 1,148 wounded and about 2,100 taken out of action by disease and non-combat injuries: trench foot was the most common affliction, and the majority of the non-combat casualties were exposure cases, victims of the weather and inadequate clothing.

Shemya is a small island about 4 miles (6.4 km) long near the western end of the Aleutian islands chain, 35 miles (56 km) to the east-south-east of Attu. With a maximum height of only 240 ft (75 m), this is the only island in the Aleutian islands group with large areas of flat ground, and the island was occupied without opposition at the same time as 'Landcrab' for development as a Boeing B-29 Superfortress heavy bomber base from June 1943. In the event, no aircraft type larger than the B-24 was based there during the war.