'Iceberg I to VII' was the US and British programme of carrierborne air attacks on the Japanese positions in the islands of the Sakishima-gunto (26 March/25 May 1945).

When Vice Admiral Sir Bernard Rawlings’s British Pacific Fleet arrived in the anchorage of Manus island, in the Admiralty islands group, on 15 March 1945, it found waiting for it just 27 out of the 69 ships of its fleet train: the other ships had been delayed by communist-inspired strikes in the docks of Sydney, New South Wales.

After the decision had been taken to incorporate the British Pacific Fleet into Admiral Raymond A. Spruance’s US 5^th Fleet as its Task Force 57, the British ships replenished and left for Ulithi atoll in the Caroline islands group, where they arrived on 19 March. Meanwhile, TF58 (Fast Carrier Task Force) had been attacking targets in the Bonin islands group in support of 'Detachment', and also in Kyushu and Okinawa. The intention was to destroy as many Japanese aircraft as possible before the launch of the 'Iceberg' landing on Okinawa. The US carrierborne aircraft destroyed great numbers of Japanese aircraft in the air and on the ground, but on 19 March three fleet carriers suffered severe damage off Kyushu: Intrepid and Wasp were sufficiently damaged to prevent their participation in the early stages of 'Iceberg', and Franklin lost more than 700 men killed by bombs and the ensuing fires, and was too badly damaged to see further service in World War II.

At this time TF57 was centred on the fleet carriers Illustrious, Indefatigable, Indomitable and Victorious, supported by the battleships Howe and King George V, the light cruisers Swiftsure and Gambia, the light anti-aircraft cruisers Argonaut, Black Prince and Euryalus, and 11 destroyers. This force left Ulithi on 23 March with orders to attack and render inoperative the Japanese airfields in the Sakishima-gunto while the US forces secured first the Kerama-retto group, some 15 miles (24 km) to the west of Okinawa’s south-western tip, and Okinawa itself.

Lying south-west of the main Ryukyu group, the Sakishima-gunto comprises two groups of islands which together constitute the extreme south-western tip of Japan, and on the islands of Miyako, Ishigaki and Mihara there were six airfields suitable for use as staging posts for aircraft heading from Formosa to Okinawa. TF57’s aircraft were to make the heaviest possible attacks on these airfields, concentrating on the cratering of the runways to render them useless. The whole undertaking was schemed on the basis of two days of attack alternating with two days of replenishment.

While TF57 was replenishing, the pressure on the islands' airfields was maintained by the US Task Group 52.1.3, comprising the escort carriers Santee, Suwanee, Chenango and Steamer Bay. With their smaller aircraft complements, the escort carriers were not as capable as the British fleet carriers, a fact which became evident as the Japanese counterattacked in mid-April.

On 26 March TF57 launched 'Iceberg I' from a position some 100 miles (160 km) to the south of the Sakishima-gunto, attacking the airfields on the two main islands. For this first attack the Grumman Avenger bombers each carried four 500-lb (227-kg) bombs to crater runways and destroy installations such as hangars, buildings and fuel dumps, while Indefatigable's Fairey Firefly attack fighters used cannon and rockets against the heavy anti-aircraft emplacements. Vought Corsair and Grumman Hellcat fighters provided escort and combat air patrol over the target area, and strafed targets of opportunity during and after the bombing attacks.

Combat air patrol over the fleet was provided largely by Supermarine Seafire fighters, whose limited endurance reduced their significance as escorts, but whose good performance, especially in climb, offered potent CAP capability. Avenger attacks were flown at a rate of about four per day, with up to 40 aircraft involved in each. Some squadrons flew sorties by single Avengers, attacking targets of opportunity. Corsair and Hellcat sorties were also flown in the dive-bombing role, and the result was that the Japanese had little if any period of respite between dawn and dusk.

Despite the British effort, the airfields proved to be unrewarding targets: the runways were built of crushed coral, of which there was an unlimited supply, and were easily repaired overnight. The Japanese anti-aircraft fire, of several calibres, was intense and accurate, and the Japanese proved themselves skilled in the creation of 'flak traps' with unrevetted or carelessly camouflaged dummy aircraft as bait. Thus, of 26 aircraft claimed as destroyed on the ground, mainly by the Corsair and Hellcat fighter-bombers, as many as 14 were probably dummies and six British aircraft were lost to anti-aircraft fire.

Japanese reconnaissance aircraft managed to located TF57, but the combat air patrol was unable to intercept them. The British also lost 11 aircraft in accidents, but the losses were made good by the replenishment escort carriers during refuelling periods, which also provided aircrews with a time to rest. Aircrew losses were comparatively light as a result of the first-class rescue service provided by US submarines on 'lifeguard' duty, destroyers from the fleet screen and the two Supermarine Walrus amphibians carried by Victorious specifically for this purpose.

Fighter cover for TF58 (the Fleet Train) was provided by the Hellcat fighters the assault escort carrier Speaker, but during replenishment periods the fleet carriers provided Avenger anti-submarine patrols, and also maintained four fighters at readiness on deck to back up the combat air patrol from the escort carrier. A typhoon warning resulted in TF57 spending three days on it first replenishment.

On 31 March, one day before the start of 'Iceberg' proper, TF57 was back on station and once more making attacks on the Sakishima-gunto’s airfields. On 1 April the Japanese began to react strongly with conventional bombing attacks in combination with the first kamikaze attacks encountered by TF57. One kamikaze aeroplane broke through the combat air patrol and hit Indefatigable at the base of her island: instead of turning the carrier’s flight and hangar decks into an inferno, the attack resulted rather in a short inconvenience while the debris was cleared from the armoured deck, and the ship was once more operational within an hour of the attack.

TF57’s attacks continued on 2 April, the British ships withdrawing that evening to replenish. Despite several attacks on TF57, the only casualty was the destroyer Ulster, which had to be towed to Leyte following near-miss bomb damage. A further three-day operational period followed from 5 to 7 April. On 6 April TF57 once again came under attack from kamikaze aircraft, but the only damage suffered was a glancing blow on Illustrious's island, which did not impair the carrier’s operational capability.

At this point TF57 was diverted to 'Iceberg Oolong', after which the ships retired to Leyte for rest and recuperation. During this period the US Navy had been unable to maintain the required operational pressure on the airfields of the Sakishima-gunto, and as a result there had been greater Japanese air activity in the area, and the US warships off Okinawa had suffered heavily at the hands of kamikaze aircraft. Two carriers had been put out of action, three battleships damaged, seven destroyers sunk, and 13 destroyers damaged. The US escort carriers had not been able to interdict the Sakishima-gunto airfields on the same scale as TF57 and, as these bases had apparently become fully operational once more following the departure of TF57, Spruance again asked for TF57.

Despite the fact that his ships needed major replenishment and re-equipment, Rawlings agreed to another two cycles of operations, now with the essentially similar Formidable in place of the damaged Illustrious. TF57 flew attacks against Ishigaki-jima and Miyako-jima of the Yaeyama islands in the Sakashima-gunto on 17, 17 and 20 April, some 50,000 lb (22680 kg) of bombs being dropped on airfields during these three days, which also saw air attacks on Japanese landing craft.

At dusk on 20 April TF57 and TF58 departed for Leyte, the ships' bunkers almost dry and the ammunition and stores ships empty. The two task forces reached San Pedro Bay on 23 April after 32 days at sea. After seven days of laborious resupply and re-equipment, TF57 and TF58 returned to sea on 1 May.

While the British ships had been at anchor in San Pedro Bay there had been pressure for its employment off Borneo, but in view of further US losses off Okinawa Admiral Chester W. Nimitz, commanding the US Pacific Fleet, once again allocated the British force the task of suppressing Japanese air capability in the Sakishima-gunto.

Thus the British air attacks started once more on 4 May as 'Iceberg II' against Ishigaki-jima. Miyako-jima was subjected to a gunfire bombardment by King George V and Howe, whose 14-in (356-mm) shells caused great damage. However, the significance of the British ships' lack of large-calibre anti-aircraft guns and the limited numbers of their smaller-calibre weapons now became apparent, for the return of TF57 coincided with a renewed kamikaze offensive. During the morning of 4 May about 20 kamikaze aircraft attacked the British ships: eight were shot down, one by anti-aircraft fire after it had penetrated the screen and the others by fighters, and of the remainder only two reached the carriers. The first hit Indomitable aft on the flight deck, slid diagonally across the deck and went over the side; the other hit Formidable abeam the island, the favoured kamikaze aiming point. The damage was not serious, the resulting fires soon being extinguished, and although a splinter put the centre boiler room out of action temporarily, the ship’s speed did not fall below 18 kt. The damage had been inflicted at the join of four armour plates, but the two-foot dent was swiftly patched with quick-drying cement and the carrier was once again operational before dusk. As aircraft were aloft at the time of the attack, only 11 aircraft were lost on deck, and of 18 Corsairs airborne at the time, 14 were recovered on the following morning from the other carriers.

A second kamikaze raid late in the afternoon was broken up by the CAP well away from the carriers, raising the day’s number of failed kamikaze aircraft to 14, 11 of them at the hands of Seafire, Corsair and Hellcat pilots. The success of the bombardment of Miyako-jima was evident on the following day, when the attacking aircraft encountered considerably reduced anti-aircraft fire, and once more the island’s runways were cratered. Formidable's losses were made good during the replenishment of 6/7 May, and her wounded were transferred to a hospital ship.

Bad weather hampered attacks on 8 May, but on 9 May the weather was good enough for British and Japanese attacks. At about 17.00 a small group of Japanese aircraft penetrated the combat air patrol and anti-aircraft screens, and Formidable was hit once again. On this occasion she had recovered her attack aircraft following their afternoon mission, and 18 Avenger and Corsair aircraft were destroyed. The flight deck was not holed by the attack, however, so the carrier was operational again within 50 minutes, albeit with only 15 serviceable aircraft.

Another kamikaze hit Victorious near her forward lift, setting fire to the ship and damaging the lift. While firefighting was in progress a second kamikaze aeroplane hit her, but bounced off the flight deck, destroying another four Corsair fighters. These were the last kamikaze attacks on TF57.

After further replenishment on 10/11 May, another pair of two-day attack cycles was flown against the islands' airfields and small craft. Japanese air activity had reduced after the major raids of 4/9 May as TF58 was again striking airfields on Kyushu. Anti-ship attacks in the waters of the Sakishima-gunto with good results. While Formidable was being replenished on 8 May an accident on the hangar deck resulted in a fire which destroyed 30 aircraft and damaged the ship. Despite the accident, the carrier was ready for action by nightfall, although very short of aircraft.

When operations were resumed on 20 May Formidable could provide only Corsair fighters for fleet and target combat air patrol. She refuelled and left on 22 May for Manus island and thence Sydney for the repairs required for her to become fully operational for the next planned series of operations.

The remaining three carriers carried out 'Iceberg VII', their last cycle of attacks off the Sakishima-gunto before they too left the area at dusk on 25 May.