Lieutenant Junior Grade Tetsuzō Iwamoto was one of the top scoring aces among Imperial Japanese Navy Air Service (IJNAS) fighter pilots. He joined the Imperial Navy in 1934 and completed pilot training in December 1936. His first combat occurred over China in early 1938. He emerged as one of the top aces of the Imperial Japan during WWII, credited with at least 94 aerial victories including 14 victories in China. Subsequently, he flew Zeros from the aircraft carrier Zuikaku from December 1941 to May 1942, including at the Battle of the Coral Sea. He was Nicknamed Zero Fighter Ace Kotetsu “Tiger Tetsu”.
In late 1943, Iwamoto’s air group was sent to Rabaul, New Britain, resulting in three months of air combat against Allied air raids. Subsequent assignments were Truk Atoll in the Carolines and the Philippines, being commissioned an ensign in October 1944. Following the evacuation of the Philippines, Iwamoto served in home defense and trained kamikaze pilots.
As a result of the Japanese use of the British naval practices, the IJNAS scoring system was based on the system the Royal Navy and the Royal Air Force (RAF) adopted from World War I until World War II. This system differed from the scoring system used by some other nations during World War II. Tetsuzo Iwamoto was one of the greatest air aces of the Imperial Japanese Navy. During his career, as per his personal records in his diary he is supposed to have achieved 242 air victories, 14 in China, 202 confirmed in the Pacific, 26 shared victories and 27 unconfirmed victories. He is supposed to have damaged two planes and destroyed two on the ground. Research by academics surnamed Izawa and Hata in 1971 estimated his score at about 87. Irrespective of the scoring system, Tetsuzō Iwamoto was the Japan’s top ace. Iwamoto was known as the Chūtai leader (Flying Company, squadron of 8 to 16 fighters). Iwamoto was one of few survivors of the IJNAS through the war. He fought over the Indian and the Pacific Ocean from north to south, and trained young pilots even in the last months of the war. Like many Japanese veterans, Iwamoto was reported to have fallen into depression after the war. His diary was found after his death, claimed of 202 Allied aircraft destroyed.
Tetsuzo was the third son of the Iwamoto family, born on a border town, southern part of Karafuto (now Sakhalin, Russia) on 15 June 1916. His father was a chief police officer. Later he grew up in Sapporo, Hokkaidō, Japan. He enjoyed skiing in his elementary school days. When he lived in Sapporo. When he was 13, his father retired and Tetsuzo moved with his family to his father’s hometown, Masuda, Shimane Prefecture. He studied at the Prefectural Masuda Agricultural and Forestry High School. His favorite school subjects were mathematics and geometry; in these subjects, he always scored very high. Whilst he was a gifted student both academically and physically, his popularity with his teachers was poor due to his insubordinate, rebellious and sometimes outright rude nature. He was otherwise an active and nimble boy. He joined a school club brass band as a trumpeter. Another hobby was growing plants and flowers. He helped local fishermen in the fishing season, going out to the sandy beach early in the morning and driving fish into the nets. He was regarded as the most opinionated student in his school, and often talked down his teachers in discussions, which was considered impolite.
Chooses a Military Career
Iwamoto started his military career in 1934 after he graduated the school at 18. Following the advice from his parents to study while young, Tetsuzo left for a large city where he was supposed to take a college entrance examination. He, however, secretly applied for and passed the examination for acceptance as an Imperial Japanese naval airman 4th class, and was promoted to 3rd class 5 months later. His parents were very disappointed, for they became reliant upon Tetsuzo rather than his eldest brother, who was already studying at some university in a large city and would not return to Masuda.
Gets Enrolled For Flight Training
In 1936, when he was a naval mechanic 2nd class and a crewman on the light aircraft carrier Ryūjō, he studied hard and passed the difficult IJNAS exam, taken by thousands of applicants. He was enrolled in the class 34th Sojyu-Renshusei flight trainee program for naval petty officers and sailors. He graduated as one of the select 26 young aviators of the class 34th in December of that year.
In April 1936, he was sent to Kasumigaura-Ku as a probationer. While his training going on November 1, 1936, he was promoted to naval mechanic 1st class. Finally on December 26, he graduated 34th class of Sojyu-Renshusei, was promoted to airman 1st class (old rank name of pre-war Japan, equivalent to senior airman). During flight training school at the Tomobe branch of Kasumigaura-Ku his fighter course instructor was the famous Chitoshi Isozaki.
Joins Naval Air Group
In December 1936. Iwamoto entered Saeki Kōkūtai Naval Air Group, which was based both at land and onboard a carrier, for 6 months of advanced training. After this he joined Omura Kōkūtai on July 16, 1937 for operational training. He had tough training there from senior pilots including Air Petty Officer 1st class Toshio Kuroiwa, who was the IJNAS legendary dogfight master pilot. Tetsuzo Iwamoto had to wait for operational debut till February 10, 1938.
The Second Sino_japanese war was already on. After combat training, on February 10, 1938, Tetsuzō Iwamoto was led by his leader APO 1/C Toshio Kuroiwa, flying for two and a quarter hours over the China Sea from Omura Airbase at Kyūshū Japan, ferrying to the airfield outside of Nanjing China. Tetsuzo’s ability as a fighter pilot was recognized by all on his first air mission with his squadron, the 13th Flying Group on February 25, 1938, over Nanchang, China. This Flying Group was highly regarded and was famed as the Nango Fighter Squadron, named after its former squadron leader, Mochifumi Nango, who had showed considerable courage and conspicuous leadership.
First Combat Mission – Four Victories
On February 25, 1938, his squadron’s fighters escorted bombers Type 96 land-based attack aircraft. 16 Chinese fighters attacked the formation, and the squadron’s leader Lieutenant Takuma was lost on this mission. Iwamoto described his first combat in his notes. During the escort mission, the squadron was intercepted by sixteen I-15s and I-16s at an altitude of 5000 meters. Iwamoto claimed 4 victories (1 probable) in the combat. He secured his first victory by firing when within 50m of the enemy fighter. He first saw white smoke, then the enemy burned up and crashed. He was then at an altitude of 4000 m. When he looked back, there was an enemy fighter just behind him. He instantly made a Split S maneuver and narrowly escaped.
He got his second victory against an I-15. He saw it below him, turned and attacked from its 6 o’clock high. When it was hit, it climbed sharply and went spinning downward out of control and crashed into the ground. He kept his altitude of 4,000 m. He got an I-16 at the top of its roll in his gunsight and fired a burst, its engine burning and out of control; Tetsuzo lost sight of it before it crashed, and he reported this as probable. Another I-15 came down to him from 12 o’clock ahead. Both made a climb and were soon in a dogfight. The I-15 tried to break free of him and made a straight dive. That action made it easier for Tetsuzo to aim. He downed this I-15 on farmland near the airfield. He was flying at an altitude of 2000 m.
Above him, many enemy fighters were maneuvering. He found one of them coming down with landing gear down. He chased it to an altitude of 200 m and fired a burst. The I-16 was surprised and made a split S maneuver, but crashed at a corner of the airfield. This was his 4th victory.
Anti-aircraft guns started firing heavily, and he found himself in an intense barrage of flak. Rushing to escape at full throttle with a number of enemy fighters behind him, he succeeded in returning safely from the battlefield. His section leader Kuroiwa with whom he had separated had already returned to the Wuhu airfield, Anhui China, waiting for his return. Kuroiwa scolded Tetsu severely for the rash attacks he made on the day.
13th and 12th Flying Groups Merge
On 22 Mar 1938, the 13th Flying Group Fighter Squadron was merged with the 12th Fighter Squadron on March 22, 1938, where Type 96 carrier fighters for 1st Chutai had landing gear painted in red and were called “Red legs squadron” while 2nd Chutai had gear painted in blue and were called “Blue legs squadron“. On 29 Apr 1938, he fought Chinese Air Force fighters and scored several victories, and was later awarded a citation by Commander Tsukahara for his extreme courage and conspicuous gallantry in action above and beyond the call of duty as a fighter pilot against intense Chinese air force.
Iwamoto Becomes Top IJNAS Ace in China
By Sep 1938, he had completed 82 missions, and had 14 kills on his records and had become the top Japanese IJNAS ace. His activities subsequently earned him “Order of the Golden Kite – 5th class” recommendation in 1940. In September 1938, 22-year-old Iwamoto was ordered back to Japan, where he became a member of the Saiki Air Group and appointed to a training staff.
Pacific War – Pearl Harbour & Carol Sea
After a tour as an instructor, Petty Officer First Class Iwamoto returned to the front line onboard the carrier Zuikaku, now flying the legendary A6M ‘Zero’ fighter. Iwamoto was airborne for the day of infamy – the attack on Pearl Harbor – but flew air cover over the carrier group itself rather than escorting the actual raid. Iwamoto was heavily involved in the air war in the Pacific from the outset, regularly leading flights of A6Ms against their American, British and Australian counterparts. Iwamoto flew in the violent air engagements of the Battle of the Coral Sea in May 1942, during which Zuikaku’s air group suffered significant losses. This necessitated a return to Japan for resupply and to train replacement aircrew which resulted in Iwamoto and his comrades missing the Battle of Midway. Small team in Japan who frantically tried to train new aircrew to stem the advancing allies.
Rabaul, New Britain
After a year of instructional duties, Chief Petty Officer Iwamoto returned to the front line and joined the 253rd Air Group, flying A6Ms from Rabaul, New Britain, in November 1943. Involved in daily air combat, the experienced fighter leader led his cadre of increasingly junior and less experienced pilots against the might of the US Navy and USAAF. Whilst operating from Rabaul, Iwamoto filed claims for a staggering 142 enemy aircraft shot down.
Caroline & Philippine Islands
After withdrawing from Rabaul, Iwamoto returned to Japan in June 1944 for a brief respite from the front line, before fighting in the skies over Formosa, then transferred to Truk Atoll in the Caroline Islands and then the Philippine Islands during autumn and the winter. In November 1944 Iwamoto’s skill and leadership were further recognised when he was commissioned as an officer in the ranks of the Japanese Navy, holding the rank of Ensign. Iwamoto’s last operational sorties were flown with the 203rd Air Group, defending Kyushu and Okinawa in the furthest Southwest reaches of Japan against the long ranged B-29 attacks and the might of the US Navy’s carrier borne air power. The last few months of Iwamoto’s war were spent training kamikaze pilots at Iwakuni airfield on Honshu island.
He was best at one-vs-one dogfights. He often employed, quick roll tactic combining with skidding sideway for sudden deceleration within 1/2 quick roll to make the opponent on the tail to overshoot. Corkscrew loop (Hineri-Komi Senpō) was a short-cut or twist-in loop tactic, also called the skidding loop. He had also mastered the High and Low Yo-yo manouvres (Suichoku-Senkai Kasoku Senpō). His favourite formation tactics, was a two group linked formation attack, where one section plays offence, zooming and diving formation attack, another section plays defense, positioned on the higher altitude to cover and support the offence section. Keeping his groups underneath thick clouds to hide his formation and waiting until the small number of opponent aircraft group coming down, then diving and zooming attack with all in a formation.
Attacking the opponent formations after their mission was over and they were on the way to the regroup point, to fly back across the distance range over the sea. This tactics was taken when his own group had much fewer aircraft. Aerial Bomb attack tactic, was a twelve o’clock high vertical dive attack from the front top in inverted flight (Haimen Suichoku Kōka Senpō). It was almost vertical diving (about 60 degree) attack because the 30 kg aerial bomb needed the releasing speed over 280 knots to work timer correctly for the explosion. Inverted flight at the starting point because Zero Fighter could not keep steep angle while diving due to its high flight stability.
Another tactic that Japanese often employed was called “Send Wolf “, which essentially meant first sending a strike against US targets, and then attacking those US aircraft that got airborne after the base had been attacked by surprise. He was very good at using the 30 kg No. 3 Aerial Bomb, which was difficult to handle, although it was used against aircraft, and caused great damage.
Aerial Victories Claimed in His Diary
His own diary claimed that he had downed 202 aircraft during the Second Sino-Japanese War and the Pacific War while sharing credit with others for another 26 kills; this translated to somewhere between 80 and 90 kills based on the scoring system used by American airmen during WW2. 94 victories is what has been assigned to him.
He had claimed seven victories against Grumman F4F Wildcat (Coral Sea, 8 May 1942, and at Rabaul, late 1943; 19 February 1944 the escort fighters of Martin flying boat). His claimed four Lockheed P-38 Lightning P-38 victories, at – 4 (Rabaul, late 1943 – 1944). 48 victories against Vought F4U Corsair, plus one unconfirmed. These were at Rabaul, Mobara-airbase outskirts of Tokyo, during Operation Kikusui, Okinawa, March 10 – June 24, 1945). This was more than 1 in 4 of all F4U air-to-air losses during the Second World War. He claimed two Bell P-39 Airacobra at Rabaul in late 1943. He claimed one Curtiss P-40 Warhawk at Rabaul, late 1943. He also claimed 39 Grumman F6F Hellcat victories, that included 29 (at Rabaul late 1943 – Feb 1944; Truk 28–29 April 1944; Operation Kikusui, Okinawa, March 10 – June 15, 1945). He claimed one Republic P-47 Thunderbolt victory over Rabaul, late 1943 – 1944. He claimed one North American Aviation P-51 Mustang over Rabaul, on 19 February 1944, the Allied 2nd air-raid of the day. He claimed to have shot four British Spitfire burned on the ground, two shot over Indian Ocean on 9 April 1942. He claimed 48 US Navy’s Douglas SBD Dauntless with seven unconfirmed, (Coral Sea, 8 May 1942; Rabaul, late 1943 – February 1944; Truk 28, 29 April 1944; Battle off Formosa, 12 October 1944). He also reportedly shot down 30 Douglas SBD Dauntless using No.3 Aerial Bombs over Rabaul, in late 1943 – 1944. He claimed five Grumman TBF Avenger, with 19 uncofirmed. These were at Rabaul, late 1943 to February 1944, the Allied 6th and the 3rd final air-raid of the day to Rabaul. He claimed five Curtiss SB2C Helldiver at Rabaul late 1943 to early 1944). He also claimed five North American B-25 Mitchell medium bombers at Rabaul, starting late 1943 to 19 February 1944, during the Allied 4th air-raid of the day. He claimed two Martin B-26 Marauder American twin-engined medium bomber at Rabaul. He claimed six Consolidated B-24 Liberator heavy bombers using No. 3 Aerial Bombs and damaged two at Truk, reportedly confirmed by ground crew. He claimed one Boeing B-29 Superfortress four-engine propeller-driven heavy bomber at Kagoshima, Kyushu, Japan, April 1945. He claimed a PBY5A flying boat over Indian Ocean on April 5, 1942. He reportedly shot a Martin Mariner flying boat victory at Rabaul, on 19 February 1944. This aircraft was escorted by 12 F4Fs. He strafed three Destroyers on the night of February 5, 1944. He strafed many Landing crafts at Kerama islands, Okinawa, on night March 26, 1945. He strafed airfields Lae, Eastern New Guinea, on January 23, 1942, and Torokina, Bougainville, Solomons, on night 1944.
Air Kills Debate – Yet Greatest Japanese Fighter Ace of All Time.
Iwamoto’s final number of kills remains open to debate. A combination of the Japanese practice of crediting victories to a squadron rather than an individual, lost records and discrepancies between the confirmation process in Japan and allied nations mean that the final tally will never be known. Most sources officially credit Iwamoto with 80 kills in WW II plus 14 in China, his war diary claims 202 individual victories, 26 shared and 22 unconfirmed. An outspoken, opinionated and brash man on the ground, Iwamoto was conversely a tactically minded and cool headed aviator who favoured hit and run tactics over dog-fighting. There is a very good chance that he was, and forever will be, the greatest Japanese fighter ace of all time.
The “Zero Fighting Tiger”
Tetsuzo had reportedly flown 8,000 hrs by March 1944. He was an operational leader, cleared for solo fighter reconnaissance and attack mission across night and over ocean. He was cleared for night carrier operations. It is believed that his aircraft in the Rabaul days was dyed in pink with more than 60 shot-down marks and was well known. The nickname is the strongest Zero Fighter pilot . Also, he seems to call himself Zero Fighting Tiger .
- Sailor Fourth Class (Seaman Recruit) – June 1, 1934
- Sailor Third Class (Seaman) – November 15, 1934
- Sailor Second Class (Able Seaman) – November 2, 1935
- Sailor First Class (Leading Seaman) – December 26, 1935
- Petty Officer Third Class – May 1, 1938
- Petty Officer Second Class (Petty Officer) – November 1, 1939
- Petty Officer First Class (Chief Petty Officer) – May 1, 1941
- Chief Petty Officer (regrading of Petty Officer First Class) – November 1, 1942
- Commissioned an Ensign – November 1, 1944
- Promoted to Sub-Lieutenant upon retirement – September 5, 1945
- Order of the Golden Kite, Fifth Class – August 1, 1942
- Order of the Rising Sun, Green Paulownia Leaves Medal – Seventh Class – August 1, 1942
Iwamoto was promoted to Sub-Lieutenant on his enforced retirement from the Japanese Navy following his nation’s surrender. The Allied Occupation Forces searched for war criminals in the Japanese Officer Corps. Iwamoto was summoned twice for questioning to Douglas MacArthur’s Allied GHQ office in Tokyo. Although he managed to avoid being declared a war criminal, he was nevertheless blacklisted from public sector employment. Managers of nongovernmental businesses and local factories in his hometown also did not dare to employ him, in order to comply with the wishes of the new Allied GHQ. In general, anyone who had been an officer in the IJA or IJN was disliked by the Allied Occupation Forces.
His wife knew him as a “wartime ace pilot”, and in fact was a fan who later married through matchmaking agency. He very methodically kept all records. Japanese journalists who had promoted Japanese militarism campaign during the war started a radio program of anti-militarism postwar called Shin-Jitsu wa Kō Da (“The Truth Is This”). The program considered people such as Iwamoto the cat’s-paws of militarism. Iwamoto struggled to survive until the San Francisco Peace Conference was held, after which, in the spring of 1952, the Allied Occupation Forces finally left Japan. In 1952, Iwamoto finally obtained employment at the Masuda spinning mill of Daiwa Bōseki (since renamed to “Daiwabō” Co., Ltd).
Death Due Medical Complications
In the summer of 1953, Iwamoto developed a stomach ache. A surgeon examined him and diagnosed enteritis. It was found later to be appendicitis. After a series of operations, he complained of a backache. Doctors decided to operate on him again. For reasons which are not entirely clear, the surgical team decided to remove three or four ribs without anesthesia. This led to sepsis. Iwamoto died on 20 May 1955, at the age of just 38 years old. His wife recalled his final words: “When I get well, I want to fly again.”
Mitsubishi A6M Zero
A light and nimble fighter, the Mitsubishi A6M Zero was the first carrier based fighter capable of besting its land based opponents, and was Japan’s main fighter of WWII. The Zero’s design sacrificed protection for speed, maneuverability, and long range, on the theory that superior speed and maneuverability were protections in their own right, with long range an added bonus. The A6M came as a shock to Allied pilots when first encountered, because it could outmaneuver every airplane it faced at the time. A better dogfighter than anything the Allies had at the start of the Pacific War, the Zero’s superior performance, especially in the hands of Japan’s elite naval aviators, exceeded anything the Allies had hitherto expected from the Japanese. In the war’s early days, Japanese naval aviators flying Zeroes achieved a 12:1 kill ratio.
To counter the Zero’s advantages, American pilots adopted team work tactics such as the “Thach Weave” which required pilot pairs to work in tandem, or the “Boom and Zoom”, in which American pilots engaged the Zero only in diving attacks, as the acceleration of their heavier planes in a dive allowed them to flee if the diving attack failed. While holding considerable advantages in maneuverability and speed, the Zero’s lack of protection for either the pilot or the fuel tanks proved a steadily mounting disadvantage as the war progressed, since the heavier and more rugged American fighters could absorb considerable punishment from Zeroes, while a single machine gun burst from the American plane could disintegrate a Zero.
By 1943, attrition had thinned the ranks of Japan’s elite aviators, and the Japanese Navy’s training pipeline could not produce enough replacements of similar caliber. As a result, there were fewer and fewer Japanese pilots capable of extracting the most out of the Zero’s advantages while minimizing its disadvantages. Which was bad news for the Japanese, as the quality of American aviators was increasing, due to wartime experience as well as an extensive training program that produced capable aviators at a rate Japan could not match. That was exacerbated by the introduction of new American fighters, such as the F4U Corsair and the F6F Hellcat, that were a significant improvement over their predecessors, and proved more than a match for the Zero, with greater firepower, armor, speed, and similar maneuverability.
By 1944 the Zero was rapidly becoming obsolete, but it remained in front line service because the Japanese faced production difficulties in fielding a replacement. From its heyday at war’s beginning when it ruled the skies of the Pacific while flown by elite pilots, A6Ms were reduced by war’s end to flying kamikaze missions under the controls of barely trained novices.
List of Japanese Navy Air Force aces Mitsubishi A6M “Zero”
This is a list of Imperial Navy Air aces flying the Mitsubishi Zero fighter during the Pacific War.
- Tetsuzo Iwamoto: 94 (including 14 in China / personal diary accounts for a total of 202 kills)
- Shoichi Sugita: 70 (some sources say 80)
- Saburō Sakai: 64 (2 in China)
- Takeo Okumura: 54 (4 in China)
- Hiroyoshi Nishizawa: 36 official (102 claimed)
- Toshio Ohta: 34
- Kazuo Sugino: 32
- Junichi Sasai: 27
- Sito Origami: 10 (9 in China, 1 disputed)
- Toshiyuki Sueda: 9
Famous Japanese Units
The air unit “Kōkūtai” (air group) with most air aces, was the Tainan Kōkūtai (in Formosa). It was the most famous group. They operated from Rabaul, New Britain and acquired their legendary fame over Taihoku (The Philippines), the Dutch East Indies, Lae and Buna (New Guinea) and, in the last stages of war, in defense of mainland Japan. Saburō Sakai was another member in this unit after Dutch Indies operations, from the Denpasar base on Bali.
Others famous units with air aces were 3rd Air Corps (including Yoshiro Hashiguchi), 253rd Air Corps (with Tetsuzo Iwamoto and Hiroyoshi Nishizawa among its members), Genzan Air Group, and other groups.
The Imperial Japanese Navy Air Service, similar to the German Luftwaffe idea of organizing an “all aces” select unit Jagdverband 44 equipped with Messerschmitt Me 262A-1a jet fighters, decided to create an all-ace unit (the 343 Kōkūtai) with Kawanishi N1K2-J fighters towards the end of the conflict; this was commanded by Minoru Genda.
Information Source Credits: This Article has used information mostly from Wikipedia and other open sources. Credit is also given to Mark Barber, War Thunder Historical Consultant, a former pilot from the British Royal Navy’s Fleet Air Arm. Information was drawn from Historical Section of the War Thunder forums and the Ace of the Month series. Credit is also given to Peter Chen’s World War II Database (ww2db.com), and historycollection.com for coverage of top World War II fighters.
Lead Picture Credit: Wikipedia