Ships
- IJN Hosho Captain from 15 April 1925 · Relieved on 1 November 1926
Seizaburo Kobayashi was born in Niigata Prefecture in 1883, the fifth son of a landowner. He left middle school before graduating, qualified for the entrance examination by a special test, and entered the Naval Academy at Etajima in 1900 with the 31st class, after a period spent in China. Classmates included Koshiro Oikawa, Kiyoshi Hasegawa, Takayoshi Kato, and Ken Terajima. He graduated on 14 December 1903 and was made a midshipman that month, two months before the war with Russia. Promotion then followed the usual ladder: sub-lieutenant in September 1904, lieutenant in October 1909, lieutenant commander in December 1915, and commander in December 1919. His specialty was gunnery. In 1917 he finished the Naval Staff College course.
In the early 1920s he served on a staff whose commander-in-chief was Takeshi Takarabe and whose chief of staff was Katsunoshin Yamanashi. The Great Kanto Earthquake of September 1923 fell during that tour, and Kobayashi worked to protect Korean residents caught in the violence that followed, telling them they could be at ease. He was promoted to captain in December 1923. His first seagoing command in that rank was the cruiser Tone.
On 15 April 1925 he relieved Ryutaro Kaizu as captain of Hosho. She was the Imperial Navy's first purpose-built aircraft carrier and, through the mid-1920s, still its only one in commission. Kobayashi came aboard during a yard period that had begun in March. The work added a crash barrier just abaft the forward elevator, a net that hydraulic power could raise in a few seconds, and it was finished on 2 July 1925. The island, mast, and crane had already come off in 1924, so the ship flew her aircraft from a flush deck with the air officer stationed on a platform at the side. For the rest of his tour Hosho went on with the practical business that later carriers inherited: landing practice, trials of arresting gear, and the training of pilots and deck crews on a hull small enough that every part of the problem was visible. He was relieved on 1 November 1926 by Giichiro Kawamura.
The Hosho command took a gunnery officer into aviation, and the navy left him there. In 1929 he commanded the new carrier Akagi for a short spell and then headed the training section of the Naval Aviation Headquarters, the two jobs falling in quick succession that autumn. Promoted to rear admiral in November 1929, he took command of the Kasumigaura Naval Air Group the same month. Kasumigaura was the navy's main school for aviators. He stayed until December 1931.
Those years placed him beside younger officers who talked of a Showa Restoration. A subordinate from the Akagi days, Yasuna Kozono, shared that ground with him. Fujii Hitoshi, later a leader of the naval men in the May 15 Incident, served at Kasumigaura while Kobayashi had the group. In the October Incident of 1931, a coup stopped before it began, the plotters put Kobayashi's name forward for Navy Minister. Later accounts have treated him as a hidden sponsor of the officers who killed Prime Minister Inukai on 15 May 1932.
After Kasumigaura he was attached to the Naval General Staff for a short time, then from February 1932 served as the navy's resident officer in China. That September he moved to the same duty in Manchuria. In April 1933 he took command of the naval force stationed there and spent the next year and a half securing a place for the navy in a region the army was making its own. Promotion to vice admiral came in November 1934, with command of the Chinkai Guard District, the navy's guarded port in Korea. He held Chinkai until March 1936.
The February 26 Incident of 1936 closed his active career. The navy regarded him as a leading man of its Imperial Way faction. He was attached to the Naval General Staff from 16 to 28 March 1936 and then placed on the reserve list. He died on 22 April 1956. The months in Hosho had been the turn that carried a gunnery captain into the air arm, and the commands that followed, from Akagi to Kasumigaura, rested on that turn.