by Mark Lardas
These landings set the pattern followed in the rest of the campaign. A ring of airfields was built around Rabaul as the campaign progressed by seizing lightly defended existing Japanese airfields or landing where the Japanese were not and building airfields there. Action against heavily contested Japanese positions was limited to New Guinea itself, for reasons independent of the reduction of Rabaul.
The United States used aircraft carriers as mobile airfields several times during the campaign, attacking Rabaul and Kavieng. The most critical attack was launched on November 5, 1943. Saratoga, pictured here, participated. (USNHHC)
Japanese airfields in western New Britain were being captured. Arawe and Cape Gloucester were taken in December 1943, with their airfields operational for Allied use by January 1944. Gatsama and Talasea, in the middle of New Britain, were snapped up in April. None proved critical in the campaign, but they provided bases from which the Allies could further isolate Rabaul. In 1944 airfields were also built on the Green Islands (160 miles from Rabaul), Emirau (250 miles), and the Admiralties (375 miles). The last two were north of Rabaul. They were occupied as the campaign reached its end, largely to isolate Rabaul by completing the ring of airfields around the fortress.
Lastly, aircraft carriers provided further, mobile airfields around Rabaul. In early 1943, the United States had only one prewar fleet carrier, Saratoga, available. By fall, new construction was replacing the prewar carriers lost in 1942. In addition, two new Essex-class fleet carriers, Essex and Bunker Hill, and three light carriers (built on cruiser hulls), Princeton, Independence, and Monterey, were used to strike Rabaul or Kavieng. Carrier aircraft could hit targets up to 250 miles away, allowing for necessary reserves.
Balanced against that was the fact that aircraft carriers were extremely vulnerable to airstrikes when without fighter cover. A strike against Rabaul, especially during the period when it still had fighter protection, required commitment of the entire carrier air group, including fighters. The Navy made three carrier strikes against Rabaul, and two on Kavieng. These targeted Japanese ships, but provided a critical injection of airpower at a decisive moment.
Backing all of this was a logistical chain which ran from the West Coast to New Guinea. Every aircraft, bullet, bomb, and gallon of fuel had to be brought across the Pacific and guarded from enemy attack once in the war zone. The United States built a logistical chain which provided the Allies with the weapons and supplies they needed, as needed. Apart from occasional shortages of aircraft and warships, the assets in theater always had sufficient logistics.
Weapons and tactics
The aerial forces of the United States and its allies were relatively ineffective during 1942, despite their strategic successes. Several major naval victories were won through dive bombing, and US fighters, especially Navy and Marine Corps aircraft, proved effective in defense, particularly when radar was available to direct aircraft to the enemy. But medium-altitude bombing of both ships and airfields had been unproductive, especially by USAAF units. In early 1943 new weapons and tactics were introduced.
One of the most radical changes was in bombing doctrine. New bombing techniques were developed by the Fifth Air Force, spearheaded by its leader George Kenney. Kenney pioneered low-level attack, using two new techniques.
General George Kenney led the Fifth Air Force. A brilliant tactician, he pioneered techniques that permitted the USAAF to devastate Japanese sea and air power. (AC)
The first was skip bombing. This involved making a mast-top pass at a target ship, flying the length of a fleeing ship. Bombs were dropped as the bomber approached. If the bomb landed on the ship, it would explode, causing damage. Bombs which missed skipped along the ship’s side, exploding next to the ship, staving in the sides above and below the waterline. Kenney personally demonstrated skip bombing in an experiment in Fiji, in July 1942. That fall he had several Fifth Air Force bomb groups practicing the technique, using a wrecked ship outside Port Moresby as a training target.
This low-level technique reduced the need for a bombardier, as the pilot dropped the bombs. One of Kenney’s group commanders, Paul Gunn, was converting A-20 light bombers into strafers, adding four .50-caliber machine guns in the nose, in the bombardier’s position. Kenney had Gunn make this field modification to a squadron of B-25s, augmenting the four .50-caliber guns in the nose with four additional guns added in pods to the sides of the bomber – two on each side attached below the pilot’s seat.
The .50-caliber was extremely powerful for a machine gun, especially against unarmored targets such as cargo ships. A bullet could penetrate a cargo ship’s deck and hull plating, and punch holes through the ship’s engines. It fired 450–600 rounds per minute. A ten-second strafing pass let a modified B-25 hit a targeted ship with 600–800 rounds. Additionally the modification allowed the bomber to keep its bomb load. The B-25 became the deadliest antiship weapon in the Southwest Pacific. Soon every B-25 in the Fifth Air Force was modified into a gunship, as were most of the B-25s in Thirteenth Air Force, Marine, and Navy squadrons operating out of the Solomons.
SKIP BOMBING: HOW TO DO IT
1: B-25 spots ship, turns towards ship and dives
2: Ship spots B-25, turns away from B-25 fearing a torpedo attack
3: B-25 begins firing machine guns to suppress AA and damage ship
4: One dropped bomb hits ship, the second explodes next to it. B-25 pulls up and out
Until skip bombing was developed Army bombers had a dismal record when attacking naval targets. Skip bombers came in low (at mast-top heights) flying the length of the ship they were targeting. If the bomb fell short or long of the aim point (typically the ship’s funnel) it was more likely to hit the ship than if the attack were made broadside. If it missed left or right, it would explode next to the ship, often underwater, rupturing the hull. Bombers, typically equipped with eight forward-firing .50-caliber machine guns, would rake the ship with bullets capable of penetrating a destroyer’s turret or piercing completely through the hull of a cargo ship.
Parachute-delayed fragmentation bombs are dropped on Lakunai. This allowed low-level bombers to destroy enemy aircraft on the ground without being destroyed by their own bombs. (USNHHC)
Kenney also pioneered new ordnance types. One was the daisy-cutter, a conventional 300lb or 500lb bomb wrapped with ¼in-diameter steel wire. It was fitted with a contact fuse attached to the end of the bomb by a 6in pipe. The bomb exploded at waist height. The wire fractured into pieces between 6in and 2ft long, spraying pieces in all directions. A daisy-cutter flattened everything within 100ft, and shredded aircraft within 100 yards of the impact point. The wire flew through the air with a whistling noise, terrifying and demoralizing men who had previously witnessed its effects on their comrades. As with the gun B-25s, daisy-cutters were a field modification, developed in theater by the Fifth Air Force.
While the daisy-cutter was an effective weapon for destroying aircraft on the ground, due to its instantaneous fuse, it was difficult to use in low-level missions. There Kenney relied on two different types of ordnance, the para-frag and the phosphorus bomb.
The para-frag bomb was a 10kg (23lb) fragmentation bomb with a parachute attached. The bombs had contact fuses, but the parachute slowed the bomb’s descent, allowing up to 90 seconds between the time the bomb was dropped and the time it struck the ground and exploded. This allowed low-level bombers to conduct a strafing pass on an airfield, drop the bombs while flying over the target, and be beyond the target area when the bombs detonated. Para-frags were carried in clusters of three with a B-25 typically carrying 12 clusters. The Allies also made use of phosphorus bombs against airfields and the supply facilities around Rabaul. The white phosphorus bombs worked both as incendiaries, for starting fires, and to create smokescreens limiting the defenders’ visibility. Much of the city of Rabaul was destroyed through firebombing.
When making low-level attacks against airfields an entire squadron of 12–16 aircraft, typically B-25s, would attack in
line abreast. If multiple squadrons attacked the same airfield, each squadron attacked individually, with the waves of aircraft spaced 90 seconds to three minutes apart to ensure no Allied aircraft were destroyed by fratricide.
The Fifth Air Force also used phosphorus bombs against Japanese aircraft on the ground. A strike camera photo shows the phosphorus bombs exploding over Lakunai airfield during a November 1943 raid. Two G4Ms and an A6M fighter are targeted. (USAAF)
DEFENDERS’ CAPABILITIES
Fortress Rabaul
Doctrine
By the start of 1943, Japan had changed war objectives twice. Its original objective had been to conquer enough territory to supply Japan with its strategic needs – petroleum, rubber, food, and metals – within a defensible perimeter. The resources were located in the Dutch East Indies (petroleum and rubber) and Indochina (food). The defensive perimeter ran in an arc from Burma along the southern islands of the Dutch East Indies, New Guinea north of the Owen Stanley Range, New Britain and New Ireland, and through the coral atolls of the Central Pacific. Once this perimeter was secured it would be fortified. Japan would wait within it until its enemies wore themselves out attacking it, wearied of war, and negotiated a peace favorable to Japan.
The Mitsubishi A6M3 was a mid-war version of the Zero, distinguishable by its squared wingtips. Despite its more robust construction many Japanese pilots preferred the older but more maneuverable A6M2. Allied intelligence believed it was a new fighter, codenaming it Hap or Hamp. (AC)
Japan’s initial success led to informal revision of that objective. Instead of establishing a defensive perimeter along that line, victory encouraged them to expand the perimeter beyond the original limits. The Solomon Islands, Aleutians, and Midway were added. The offensive in New Guinea was expanded to include the southern half of the island. Japan even briefly considered invading Australia. Instead of waiting for the Allies to tire of attacking a fortified defensive perimeter, Japan would keep pushing the enemy back until it sued for peace.
That decision led to disaster. Between May 1942 and January 1943 Japan experienced a series of severe setbacks as a result of expansion beyond its original perimeter. This included the loss of four fleet carriers at Midway, and a long unsuccessful battle to hold Guadalcanal. By January 1943, Japan had reverted to its original objective of fortifying a defensive perimeter and holding it until the Allies wore themselves out attacking.
For Southeast Area, holding Rabaul and the north coast of New Guinea was critical. To Japan they seemed the keystones in their defensive arc. Without them, especially Rabaul, the arc would crumble. The Allies were on the advance in New Guinea, threatening Japan’s defensive perimeter. They were also advancing up the Solomons, but these islands – except possibly Bougainville – fell outside Japan’s defensive ring. Imperial Headquarters chose to pursue a policy of active defense in the Solomons and aggressive offensive in New Guinea in 1943. This resulted in a drawdown of Army assets in Rabaul, especially aircraft, as resources were transferred to New Guinea. By October, virtually all Imperial Japanese Army aircraft had left Rabaul, and its aerial defense would be conducted almost exclusively by the Navy, principally the land-based Eleventh Air Fleet, assisted by the Eighth Fleet, based at Rabaul. Japanese plans for defending Rabaul consisted of keeping Allied forces as far from Rabaul as possible through a stubborn defense of the southern islands of the Solomon chain. To that end, the Japanese Navy attempted two air offensives in 1943: Operation I and Operation RO. Both were intended as crushing air operations, which would sweep Allied forces south.
Vice Admiral Jinichi Kusaka was the senior naval officer in the Southeast Area. Once Imperial Japanese Army aircraft departed to New Guinea, Kusaka commanded the only aircraft operating out of Rabaul. He held primary responsibility for Rabaul’s air defense during the Allied air offensive. (USNHHC)
Operation I took place in April 1943. The air contingents of four Japanese aircraft carriers and the remaining G3M and G4M “rikko” bomber squadrons were sent to Rabaul. Combined with the air fleet at Rabaul, this brought a force of over 350 aircraft to attack the United States at the just-taken Russell Islands. It was the largest concentration of Japanese airpower since Pearl Harbor. Japan hoped for a similar result: one or two massive airstrikes which would cripple the target. Instead the operation resulted in heavy aircraft losses by the Japanese, minor losses for the United States, and the death of Isoroku Yamamoto, Japan’s ablest admiral.
Operation RO, originally scheduled for September 1943, was delayed until October. It reprised Operation I. Again, the carrier aircraft from the Combined Fleet were sent to Rabaul with the intention of launching a single massive strike against the Allies, reversing the momentum of the Allied offensive. Operation RO became entangled in the Allied air offensive against Rabaul, which started before RO began.
Both operations highlighted the weakness of Japanese air doctrine and strategy. Both were based on a belief that a few but massive airstrikes would change the balance in a theater. This worked in the opening months of the war. Pearl Harbor crippled the US Navy. Japan gained air superiority over the Philippines with a few days’ bombing of Clark Field and other American airfields in Luzon. The Indian Ocean Raid of March 31–April 10, 1943 had chased the Royal Navy out of the Bay of Bengal and the western Indian Ocean.
It had worked because those attacks were made against foes that were surprised or lacking reserves. By 1943, however, the Allies were practiced in meeting air raids, and had enough aircraft to meet even massive Japanese air raids on equal terms and replace losses incurred. Since defeat was unthinkable, Japan kept using its previous strategy of bold decisive strikes to overwhelm the foe. It was a triumph of hope over experience.
Faulty Japanese intelligence was another weakness. Excessive assessment of damage to enemy forces was routinely accepted. Attacks were prematurely discontinued because objectives had seemingly been achieved. Since the reported number of ships sunk or aircraft downed often exceeded what the opposition was estimated to have, further operations were thought unnecessary.
Japan knew that it could not win a war of attrition, but it was forced into one at Rabaul. Throughout 1943 aircrew were lost at rates higher than Japan could replace them. In part this was due to Japan’s exacting training standards. Competent trainees who were not brilliant performers were washed out – a practice which continued after the war started. This left Japan without men to fly the aircraft available.
By 1943 it was apparent to Japan that it could not win a quick victory, and was incapable of winning an attrition battle. At Rabaul Japan’s strategy was simply to refuse to concede the possibility of defeat and keep throwing inadequate numbers of fighters at an ever-increasing number of attacking bombers and fighter aircraft. Japan achieved its objective of holding Rabaul, but only at the sufferance of its opponents and to the detriment of its efforts elsewhere.
The Japanese capability to defend Rabaul depended on the same three factors as the Allies: aircraft, facilities, and weapons and tactics. Rabaul was jointly defended by the Imperial Japanese Navy and the Imperial Japanese Army. These two services cooperated closely, if not always gladly, at Rabaul. The Emperor ordered cooperation, and in Imperial Japan the Emperor’s command was literally the word of God. Despite losses in 1942, formidable capabilities remained to the Japanese at the start of the campaign.
Admiral Mineichi Koga commanded the Japanese Combined Fleet stationed at Truk during the siege of Rabaul. In that role he could send aircraft and warships to reinforce Rabaul’s permanent garrison. (USNHHC)
The two services conducted a joint air defense of Rabaul through much of 1942 and 1943 with both Army and Navy aircraft patrolling the skies over the Gazelle Peninsula. Aircraft losses in New Guinea in August and September 1943 forced realignment. To make up the shortfall in New Guinea, Army aircraft in New Britain were transferred to New Guinea. Sending one service simplified supply, and the shorter-ranged Army aircraft were more useful on New Guinea. The Army continued to play an
important role in the air defense of Rabaul as it operated over half of Rabaul’s antiaircraft guns.
Japanese defensive capabilities were bolstered by generous stocks of fuel, food, ammunition, and supplies. Rabaul was to be the supply depot for the future Japanese expansion which never occurred, and so throughout 1942 these supplies had poured in. They were available for its defense. Rabaul was the most heavily defended Japanese citadel in the Southwest Pacific and one of the most heavily defended in the Pacific. But Japan’s biggest weakness was its lack of replacements, in aircraft, pilots, and supplies. It had to fight with what was on hand.
Aircraft
The Japanese had nearly 300 land-based aircraft stationed on Rabaul when the Allied campaign to reduce Rabaul began. Up to 300 additional carrier aircraft from the Combined Fleet were available. These reserve aircraft, normally at Truk, were shuttled in as needed. Six types of aircraft defended Rabaul. These included:
Mitsubishi A6M (“Zero,” “Zeke,” “Hamp”)
This was the famous (or infamous to the Allies) Mitsubishi Reisen (Zero). The Zero dominated the Pacific in 1941 and 1942, so much so that the Imperial Japanese Navy delayed developing a replacement. By 1943 it was becoming outclassed by new Allied fighters, especially the F6F and F4U. Two types of Zeroes were used at Rabaul, the A6M2 (called “Zeke” by the Allies) and A6M3 (Hap or Hamp). Both types were armed with two 7.7mm machine guns and two 20mm cannon (Type 99-1 for A6M2 and Type 99-2 for A6M3). Both versions had a service ceiling of 32,000ft and a top speed of 332mph. The A6M2 had a range of 1,600 miles. The A6M3 had a shorter range, but was still capable of ferrying from Truk to Rabaul and of providing airfield defense. Although the A6M3 had a more powerful cannon and better protection, Rabaul pilots preferred the older A6M2 due to its greater maneuverability. There were 150 A6Ms stationed at Rabaul at the start of the campaign. These were frequently reinforced by carrier force aircraft.