'Bankrate' was the US overall scheme by Admiral Chester W. Nimitz’s Pacific Ocean Areas command for the capture of the key elements of the Marshall islands group (January/February 1944).
The main components of this strategically important plan were 'Flintlock', 'Catchpole' and 'Hailstone'.
The Marshall islands group comprises a pair of parallel atoll chains extending some 800 miles (1285 km) from south-east to north-west. The group lies 2,200 miles (3540 km) to the south-west of the Hawaiian islands group, and in 1941 accommodated Japan’s most eastern bases. As a result, the attention of Admiral Husband E. Kimmel, commander-in-chief of the US Pacific Fleet, was fixed on this island group as war approached, rather than on the open waters to the north of the Hawaiian island group, from which the 'Ai' attack on Pearl Harbor was in fact delivered.
The Marshall islands group includes numerous excellent anchorages, but an astonishingly small land area totalling just 70 sq miles (181.43 km˛): the islands' average height above sea level is just 7 ft (2.1 m) and their maximum elevation of 34 ft (10.4 m). However, this was enough for a handful of airfields. The native population in 1935 was about 10,000, and there were 490 Japanese.
Japan had seized the Marshall islands group from Germany during World War I, and retained control after the war’s end in 1918 under a League of Nations Class C mandate that forbade any military fortification. When Japan withdrew from the League of Nations, she nonetheless retained control of the islands and refused to allow foreigners to visit the area. This led inevitably to rumours that the islands had been heavily fortified, but in fact nothing but airfields and seaplane ramps had been constructed in the period before December 1941. The fact of the matter was that the Japanese could not decide whether to make the Marshall islands group the core of their outer line of defence or to abandon the Marshall islands group and concentrate on the fortification of the Mariana islands group farther to the west. As a result, neither was adequately fortified when the US Central Pacific offensive swept to the west.
The administrative centre of the Marshall islands group was located on Kwajalein, but there were also significant facilities at Maloelap, Wotje, and Jaluit.
US carrierborne air forces struck at the Marshall islands group on 1 February 1942. The operation was the brainchild of Admiral Ernest J. King, the chief of naval operations, who from 2 January 1942 exerted strong pressure on Admiral Chester W. Nimitz, now commanding the Pacific Fleet, to seize the operational and strategic initiative rather than use his carrier task forces defensively to cover his main base at Hawaii and the sea lanes to Australia. Captain Charles H. McMorris, head of the Pacific Fleet’s war plans section, developed plans for an attack on the Marshall islands group by Rear Admiral Wilson Brown with Task Force 11 (based on the fleet carrier Lexington) on 14 January and the Gilbert islands group by Vice Admiral William F. Halsey with Task Force 8 (based on the fleet carrier Enterprise) on 17 January while Rear Admiral Herbert F. Leary’s Task Force 14 (based on the fleet carrier Saratoga) covered Oahu and Rear Admiral Frank J. Fletcher’s Task Force 17 (based on the fleet carrier Yorktown) covered a reinforcement convoy to Pago Pago. Still wary of running risks of this magnitude, Nimitz asked for the advice of Vice Admiral William S. Pye, the commander of the Pacific fleet’s Battle Force, who recommended that the raids take place after Fletcher had finished escorting his convoy. The plans had to be further modified after Saratoga was torpedoed and severely damaged on 11 January.
The plan which was finally adopted called for Halsey to make a daring penetration of the Marshall islands group and launch his aircraft from a point practically within visual range of the north part of Wotje atoll. Most of Halsey’s aircraft were to attack Kwajalein while Spruance led a cruiser force to undertake a gunfire bombardment of Wotje and a third cruiser struck at Maloelap. Farther to the south, Fletcher was simultaneously to launch attacks against Jaluit, Mili and Makin in the northern part of the Gilbert islands group. Because intelligence showed the Japanese carriers were moving to the south of Truk, Brown was assigned to make a preliminary raid on Wake while the tactical door was ajar. King was anxious for the raids to take place as soon as possible, to be driven home with vigour, and the carriers then to pull back rapidly so that they could prepare to counter the Japanese move to the south.
Brown’s raid had to be cancelled when his oiler, Neches, was sunk by a submarine on 23 January and no other oiler could be made available on time. However, the other raids went ahead. Enterprise and Yorktown each refuelled at 24.00 on 29 January and then made their final approaches the next day and night, crossing the international date line to reach their launch points early in the morning of 1 February. Halsey’s force came within a very narrow margin of detection on 31 January when a Japanese scout floatplane came within 30 miles (48 km) on radar but failed to detect the force. Complete surprise was therefore achieved by both task forces.
Fletcher’s force ran into very poor weather, with overcast and squalls, but he was able to launch 17 Douglas SBD Devastator dive-bombers and 11 Douglas TBD Devastator torpedo bombers against Jaluit, and 14 SBD dive-bombers against Makin and Mili. The attack on Makin damaged the gunboat Nagata Maru and destroyed two seaplanes, while the attack on Mili found no worthwhile targets. The attack on Jaluit ran its highly difficult weather and several of the aircraft located no target, and the remainder inflicted only light damage on the 8,90-ton transport Kanto Maru. Eight aircraft were lost, but Fletcher’s destroyer screen was able to rescue four men of their crews. Japanese search aircraft soon located Fletcher’s force (though one was shot down within sight of Yorktown) despite the terrible weather, but there was no counterattack. Fletcher considered waiting another day in hopes that the weather would improve enough for another attack against Jaluit, but was recalled by Halsey.
Halsey had benefited from better weather and had accordingly enjoyed greater success. Some 15 ships were claimed sunk at Kwajalein and there was extensive damage to shore facilities at Wojte and Maloelap, though the actual damage was three small auxiliary vessels sunk, two old warships and four transports damaged, and 15 aircraft destroyed, at the cost of six of Halsey’s fighters, light damage from a bomb hit on the heavy cruiser Chester, and very light damage to Enterprise from a bomber which only just missed crashing into her flight deck. Impressed with the ferocity of the Japanese counterattacks, Halsey decided that a speedy withdrawal was in order.
The US attacks inflicted only moderate damage, but provided valuable combat experience to the US air groups, served to bolster Allied morale, and badly shocked the Japanese. Admiral Isoroku Yamamoto quietly pulled the fleet carriers Shokaku and Zuikaku back to Japan, but the remaining four Japanese fleet carriers continued operations to the south. Nimitz decided that the raids had given him sufficient breathing space to send Saratoga to the US west coast for repairs and to recall Yorktown and Enterprise to Pearl Harbor for much-needed refit and resupply.