Lieutenant Junior Grade was one of the top scoring aces among Imperial Japanese Navy Air Service (IJNAS) fighter pilots. He entered 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 World War II, credited with at least 80 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. Iwamoto decorated his planes with victory markings of cherry blossom flowers, with a single or double blossom flower referring to a shot down enemy fighter or bomber aircraft respectively.
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. Research by academics surnamed Izawa and Hata in 1971 estimated his score at about 80 or more than 87. In December 1993, Izawa wrote that Iwamoto was virtually the top ace of the IJNAS.
As of mid-1944, there remained only two IJNAS fighter pilots who were credited with over 100 victories. Depending on various totals cited, Tetsuzō Iwamoto or Hiroyoshi Nishizawa was 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 from the early part of the Second World 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, with claims of 202 Allied aircraft destroyed.
Early life
Tetsuzo was the third son of the Iwamoto family. He was born on a border town, southern part of Karafuto 15 June 1916, later grew up in Sapporo, Hokkaidō, Japan. He enjoyed skiing in his elementary school days. When he lived in Sapporo, his father was a chief police officer.
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 As on his school report.
He was 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 talked down to his teachers sometimes in discussions, which was very impolite for a school student in pre-war Japan. He was regarded as the most opinionated student in his school.
Starting 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.
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 Sōju-Renshūsei (Sōren means flight trainee program) for naval petty officers and sailors. He graduated as one of the select 26 young aviators of the class 34th Sōju-Renshūsei (flight trainee program) in December of that year.