Ships
- IJN Sazanami Captain from 10 September 1941
- IJN Hamakaze Captain from 20 July 1942
Commander Hiroshi Uwai was a destroyer officer of the Imperial Japanese Navy. On 10 September 1941 he became captain of Sazanami, a special-type fleet destroyer of Destroyer Division 7. The division also included Oboro, Akebono, and Ushio. He took command in the last months of peace, with the fleet already preparing for operations far from home waters.
For the Hawaiian operation that opened the war, Sazanami and Ushio were detached as a bombardment unit and sent against Midway. On the morning of 7 December 1941 the two destroyers closed the atoll and shelled the installations ashore. Coastal guns answered, and both ships turned away. Uwai's first wartime action was that shelling, carried out on the same day Japanese carrier aircraft struck Pearl Harbor.
After the Hawaiian operation Sazanami returned to fleet duty, and Uwai remained her captain into the summer of 1942. On 20 July 1942 he left Sazanami and became captain of Hamakaze, relieving Tsuneo Orita. Hamakaze was a Kagerō-class destroyer of Destroyer Division 17, in company with Urakaze, Isokaze, and Tanikaze. She was already a veteran carrier escort, having screened the striking force for the attack on Pearl Harbor and at the Battle of Midway that June.
Uwai's first fleet battle in Hamakaze came on 24 August 1942 at the Battle of the Eastern Solomons, where Destroyer Division 17 formed part of the screen around the carriers. On 26 October 1942, at the Battle of Santa Cruz, Hamakaze was again with the carriers while aircraft from both sides struck the opposing flight decks. In those actions the destroyers held station at speed, fired on aircraft that reached the formation, and stood by damaged carriers. Kazue Maekawa served with him among the destroyer commanders of that force.
After Santa Cruz the carrier groups drew back to rebuild their air groups, and Hamakaze stayed with them on the passages between the combat area, Truk, and Japan. Officers of his destroyer service also included Matsuji Ijuin and Akiji Suga. His two commands had taken him from Sazanami on the first morning of the Pacific War to Hamakaze in the carrier battles of the Guadalcanal campaign.