Ships
- IJN Satsuki Captain from 26 May 1943
Shirō Koizumi was a lieutenant commander of the Imperial Japanese Navy and a graduate of the fifty-seventh class of the Naval Academy. He commanded three destroyers in the middle of the Pacific War: Sanae, Hatakaze, and, for the summer of 1943, Satsuki. With Satsuki he took part in the transport runs that tried to hold the central Solomons against the American landings on New Georgia, and he was on the scene at the loss of Nagatsuki in the Battle of Kula Gulf.
Nothing is known of his birth, family, or schooling.
He belonged to the fifty-seventh class of the Naval Academy at Etajima. The record shows him as a lieutenant commander by October 1941, in command of a destroyer, and nothing earlier in his service has been found.
On 1 October 1941 he was in command of the destroyer Sanae, a Wakatake-class ship that the Japanese account says was used mainly on convoy escort after the war began. He held her until 25 October 1942, when he was transferred. On 10 November 1942 he took over the destroyer Hatakaze, a ship of the Kamikaze class attached to the Yokosuka naval district. On 2 March 1943, while she was at Yokosuka, depth charges exploded at the stern during maintenance. The stern settled, a fire broke out, and about forty men were killed or wounded. He commanded her until 26 May 1943, when he was posted to Satsuki.
Satsuki was in the Solomons and the Bismarcks with the 22nd Destroyer Division. On the afternoon of 28 May, two days after he took command, she and Nagatsuki left Buin for Kolombangara on a troop run and both ran aground on a reef southeast of Bougainville. Both were refloated the next morning and returned to Buin, where Satsuki was judged unable to continue. She went to Rabaul for repairs that lasted until 3 June. On 4 and 8 June she made runs to Tuluvu on New Britain. On 26–27 June, with Mochizuki and Yūnagi, she ran from Rabaul by way of Buin to Kolombangara. On 2 July she took part in the bombardment of Rendova.
On 4–5 July she sailed with Niizuki, Nagatsuki, and Yūnagi on a troop run toward Kolombangara that was abandoned when the group met American ships in the entrance to Kula Gulf. The next night, 5–6 July, she was in the Battle of Kula Gulf. After the battle she removed the division commander, Captain Kunizo Kanaoka, from Nagatsuki, which had gone hard aground, and tried without success to tow her off. On 9 July Satsuki led a troop run to Kolombangara with Mikazuki, Matsukaze, and Yūnagi and landed 1,200 troops and 85 tons of supplies at Vila. On 12 July she landed troops during the Battle of Kolombangara and saw no action. On 17 July American aircraft raided the Shortlands, and near-misses and strafing damaged her enough to cut her best speed to twenty knots. She went to Rabaul for emergency repairs.
At the end of July she escorted a convoy from Rabaul to Truk. In August she escorted the carrier Taiyō from Truk to Yokosuka and went on to Kure, where she was refitted: her number four main gun was removed and replaced by two triple 25-millimeter mounts, with other light weapons added. On 1 September 1943 Lieutenant Commander Tadao Iino relieved him.
The sources checked do not record Koizumi's next post or whether he survived the war.