Operation Aob

'Aob' was a Japanese sub-operation within 'Al' for the seizure of Kiska island in the Aleutian islands group by the 500 naval troops of Captain Takejo Ono’s 3rd Special Landing Party(6/7 June 1942).

Kiska is the westernmost of the Rat islands group in the Aleutian islands chain. Located 610 miles (980 km) to the west of Dutch Harbor on Unalaska island, Kiska is so isolated and so inhospitable that it had no permanent inhabitants in 1941. However, Kiska Harbor was probably the best natural anchorage in the western part of the Aleutian islands chain, with room for the anchorage of 40 ships. The island itself is 22 miles (35 km) long and has an area of 110 sq miles (285 km˛), and its highest elevation is the 3,966-ft (1209-m) Kiska volcano on the island’s north-eastern end. The shores are rocky, steep, and backed by cliffs in most locations, leaving only a few small beaches suitable for landing operations.

After landing before dawn on 7 June from the 5,863-ton Borneo Maru, the 500 or so Japanese troops of the 3rd Special Landing Party quickly killed two and captured seven of the other eight of the island’s sole inhabitants, who were 10 men of a US Navy meteorological party: the eighth man surrendered after remaining at large on the island for 50 days.

So generally abysmal is the weather in the western part of the Aleutian islands group that it was not until 10 June that an US reconnaissance flight was able to confirm that the island had indeed been invaded.

After the initial landing, another 2,000 men arrived in Kiska Harbor and Rear Admiral Monzo Akiyama assumed command of the garrison. In December 1942 the Japanese delivered anti-aircraft and engineer units, as well as a small number of naval troops, and in the spring of 1943 command of the Japanese garrison was assumed by the Imperial Japanese army in the person of Lieutenant General Kiichiro Higuchi, under whose control the island’s Japanese population grew to anything between 5,183 and 5,500 military and civilian personnel. The Japanese built a large underground base and improved the harbour, but were not able to complete an airfield of any practicality.

An unusual consequence of 'Aob' and its partner 'Aq' against Attu island, shortly before the US 'Cottage' undertaking to recapture the island, was the Battle of the Komandorski Islands (known to the Japanese as the Battle off Attu Island) on 27 March 1942. Knowing as a result of 'Ultra' intelligence that the Japanese planned to run to this and other remote island bastions in the northern Pacific a supply convoy of three large merchant vessels escorted, in a manner unknown to the Americans, by every available warship of Vice Admiral Boshiro Hosogaya’s 5th Fleet, Northern Force, the US Navy despatched Rear Admiral Charles H. McMorris’s Task Group 16.6 to intercept the convoy.

TG16.6 comprised the heavy cruiser Salt Lake City, light cruiser Richmond, and destroyers Coughlan, Bailey, Dale and Monaghan. The Japanese escort comprised the Northern Force (heavy cruisers Nachi and Maya, light cruiser Tama, and destroyers Wakaba and Hatsushimo) and Rear Admiral Tomoichi Mori’s D Convoy with three transport vessels (7,399-ton Asaka Maru, 7,189-ton Sakito Maru and 4,958-ton Sanko Maru) escorted by the light cruiser Abukuma and destroyers Ikazuchi, Inazuma and Usugumo.

At 05.00 on 26 March, the Japanese column of eight warships and the transports Asaka Maru and Sakito Maru was heading to the north north with the transports located toward the rear of the column, followed only by Inazuma, which thus brought up the rear. On a parallel course, about 23 miles (37 km) to the south-east of the Japanese column, was TG16.6 in two columns with Coughlan, Richmond, Bailey and Dale 6 miles (9.5 km) to port of the main column comprising Salt Lake City and Monaghan.

At 05.00, the radar of two of the US Navy ships picked up at least five ships, 8 to 14 miles (13 to 22 km) to the north. At once the US group began moving into a single column with Bailey leading Coughlan, Richmond, Salt Lake City, Dale and Monaghan.

The Japanese force was fully alert in the hours before dawn, and Inazuma had reported the sighting of ship silhouettes at 04.00. At first Hosogaya believed that these were the destroyer Usugumo and transport Sanko Maru, which were scheduled to meet the convoy. But after a report from one of Nachi's lookouts at 05.08, other sightings followed rapidly, and at 05.15 Abukuma relayed specific information about nearby US ships. Hosogaya now knew that his force was about to be engaged, and ordered the transports to slip away to the north-west, screened by Inazuma. At 05.30 Abukuma and her destroyers turned in column to starboard to form a screen for the heavier Japanese warships. At 05.42 Nachi, Maya and Tama also turned to starboard, paralleling Abukuma's column.

At the same time, TG16.6, now with the two cruisers in line ahead and screened on each side by two destroyers, began to turn west in column in pursuit of the transports. At 05.42 each side opened fire at a range of about 20,000 yards (18290 m), and two minutes later Nachi launched two salvoes each of four 24-in (610-mm) 'Long Lance' torpedoes.

Shortly thereafter, the Japanese cruisers split into three groups. First Abukuma turned south-west, paralleling the US ships on their port quarter. Then at 05.47 Tama took up the same course, close by Abukuma's port side. Maya and Nachi held their course with 24,000 yards (21945 m) separating the two forces, thus blocking the US task group from returning to their base.

Fought at long range, the Battle of the Komandorski Islands was a duel of the heavy cruisers. Nachi and Maya, after an initial salvo directed at the outranged Richmond, concentrated on Salt Lake City; meanwhile, any aggressive move by the US cruisers could be countered by Hosogaya’s lighter forces.

McMorris was outnumbered in ships and weight of fire. Undaunted, at 05.42, he turned his column to port on a south-westerly course. At that moment Salt Lake City and Maya and Nachi opened fire at a range of about 20,000 yards (18290 m). The two Japanese cruisers continued in a long turn to starboard, still seeking to cut the US force off from its base. The manoeuvre placed Maya and Nachi in the undesirable position of making their chase astern the US ships. At 05.50 Salt Lake City scored one hit on Nachi's bridge, and two minutes later achieved another hit, this time on the Japanese cruiser’s torpedo tubes. It was inevitable, though, that Salt Lake City would suffer in this one-sided gun duel, which pitted 10 US 8-in (203-mm) guns against 20 Japanese guns of the same calibre.

Maya hit Salt Lake City's midships catapult aeroplane with an 8-in (203-mm) shell at 06.10. The US cruiser was hit again at 06.20 on her quarterdeck, probably by Nachi.

Tama had tried to close the US column, but her action report mentions makes no mention of torpedoes or shells fired. She withdrew to the north-west, placing herself between the US force and the Japanese transports.

Abukuma also closed the US ships' starboard side, but then veered in long turns to the north-west. She was engaged at 06.53 and 07.07 but not hit. Hosogaya opted for caution, wanting to protect his convoy and yet manoeuvre to destroy the US force. To do so, he continued to turn his two heavy cruisers and four destroyers to starboard until, by 06.57, they were steaming on a north-westerly course. Although Maya and Nachi were newer and faster than their main US adversary, their stern chase forced them to zigzag, both to unmask their stern turrets and to avoid ploughing into a torpedo attack. Thus they could not close the range on the US task group.

At 07.07 Maya and Nachi, 21,800 yards (19935 m) to the east of the Salt Lake City, blocked McMorris from getting at the transports. But McMorris’s concern rapidly shifted to saving Salt Lake City: at 07.02 she had begun to lose steering control, and thus her ability to chase splashes. She was hit a third time at 07.10 by a shell from Maya which went straight through the main deck into the hull below the waterline. Salt Lake City was in serious trouble and ordered a smokescreen, which was provided by her destroyers from 07.18. At 08.03 Abukuma scored one last hit on her, ruining her after gyro equipment and flooding her after engine room. Eventually the US heavy cruiser slowed as water flooded her boiler rooms, and at 08.55 her engines stopped. By this time she had turned back on a south-easterly course.

Although by then Salt Lake City was hardly visible, Abukuma, almost directly astern her, was still trying to hit her with long-range fire. Hatsushimo had also fired five heavyweight torpedoes at Salt Lake City at 08.57, while Wakaba launched five at her screen, which was now steaming east on her starboard quarter. None of the torpedoes hit.

Salt Lake City finally got under way again at 10.00, but by then the battle was over. Hosogaya’s force was headed south-west escorting the transports back to Paramushiro. Because the battle was fought at long range for nearly four hours, it is not surprising that the naval track charts of the two forces do not match. The Japanese track chart does not show the loss of way of Salt Lake City when she was most vulnerable, or record a torpedo attack by the destroyers Bailey, Coughlan and Monaghan. The US record shows that at 09.00 and 09.03 Bailey was hit twice, one shell penetrating to the electric generators, and then at 09.03 she launched five torpedoes and turned east, ordering the other two destroyers to follow her.

According to her action report, Maya was not hit, but the blast of her own guns set fire to one of her reconnaissance floatplanes. Abukuma and Tama received no damage. Nachi, however, took the brunt of the fire, mainly from Salt Lake City, and her action report records two hits at 05.55 and 08.48. Hatsushimo, Inazuma and Wakaba were not hit.

Although justifiably concerned for his transports, Hosogaya had been overly cautious: even with a decidedly superior force, he received nearly as much damage as the US ships. He never closed range to take on the crippled Salt Lake City and her protecting lighter warships. His light cruisers did not make an all-out attack, and his destroyers did not make a typical Japanese torpedo attack. The battle might easily have been a Japanese victory, and Hosogaya was retired from naval service a month later.

McMorris probably displayed courage rather than judgement in his actions and, though he did not get at the Japanese transports, he saved a heavy cruiser from a perilous situation and prevented the reinforcement of Kiska. (The date of the Battle of the Komandorski Islands is often given as 26 March as a result of the fact that the US ships used Honolulu time, appropriate to locations east of the International Date Line, but the local date off the Komandorski islands group was 27 March.)

Kiska island was bombarded on 7 August 1942 by a force of US cruiser and destroyers as a diversion from the 'Watchtower' landing on Guadalcanal.

The Aleutian phase of the war was concluded from 11 May 1943 when, bypassing Kiska, the US Army landed 11,000 troops on Attu, where there were some 2,500 Japanese troops. The fighting was bitter, ending on 29 May with the Japanese forces wiped out, except for 28 men taken prisoner.

With Attu lost, the Imperial General Headquarters decided to attempt another 'Ke' evacuation, in this instance 'Ke' (ii) from Kiska. The operation started on 26 May with the use of 13 submarines (I-2, I-5, I-6, I-7, I-9, I-21, I-24, I-35, I-155, I-157, I-168, I-169 and I-171) each making as many as three runs to extract an initial total of 820 men, but was abandoned after seven of the boats had been lost. Having no stomach for another 'Tokyo Express' undertaking based on the deployment of light cruisers and destroyers, the Japanese decided to evacuate the island by ship, and through good meteorological work and skilful execution, the troops were brought off the island without any US realisation that this had been achieved.

A Japanese task force, advised that fog would cover its approach, left Paramushiro on 21 July. Slipping into Kiska Harbor (a dangerous task in fog) at 17.40 on 28 July, two cruisers and six destroyers took off the garrison of 5,183 men in 55 minutes and were on their way back to Paramushiro.

Ignorant of the evacuation, a US invasion force of about 35,000 landed at Kiska on 15 August to find, after a two-day sweep and search operation, only four abandoned dogs. Still, the Americans had learned something important from this turn of events, a lesson also being learned in New Guinea and the Solomon islands group: by leapfrogging the Japanese positions, certain islands could be neutralised merely by being systematically isolated.