Built under the 1931 Fleet Replenishment Program, the Mogami-class cruisers were designed to the maximum limits allowed by the Washington Naval Treaty, using the latest technology.

At the time of the attack on Pearl Harbor, Mikuma was assigned to cover the invasion of Malaya as part of Cruiser Division 7 under Vice Admiral Jisaburo Ozawa's First Southern Expeditionary Fleet, providing close support for landings of Japanese troops at Singora, Pattani and Kota Bharu.

[3] In December 1941, Mikuma was tasked with the invasion of British Borneo, together with Mogami, covering landings of Japanese troops at Miri and Kuching.

At 2300 on 28 February 1942, Mikuma and Mogami, destroyer Shikinami, light cruiser Natori and destroyers Shirakumo, Murakumo, Shirayuki, Hatsuyuki and Asakaze arrived and engaged the cruisers USS Houston and HMAS Perth with gunfire and torpedoes after the Allied vessels attacked Japanese transports in the Sunda Strait.

[3] In March, Mikuma and Cruiser Division 7 were based at Singapore to cover Japanese landings in Sumatra[6] and the seizure of the Andaman Islands.

On 26 May, Cruiser Division 7 arrived at Guam to provide close support for Rear Admiral Raizo Tanaka's Midway Invasion Transport Group.

On 5 June, Admiral Isoroku Yamamoto, CINC of the Combined Fleet ordered Cruiser Division 7 to shell Midway in preparation for a Japanese landing.

Cruiser Division 7 and DesDiv 8 were 410 nautical miles (760 km; 470 mi) away from the island, so they made a high-speed dash at 35 knots (65 km/h; 40 mph).

The destroyers Arashio and Asashio of DesDiv 8, which had steamed ahead with the Suzuya and Kumano at high speed to escape the range of Midway's aircraft, were ordered by Kurita to reverse course and escort Mogami and Mikuma.

At 0630, a PBY Catalina spotted the stragglers, thanks to the massive oil trail leaking from Mikuma, and radioed their coordinates to Admiral Spruance.

Midway wasted no time after receiving the report and launched the remnants of VMSB-241 containing 12 dive bombers (6 SBD Dauntlesses and 6 SB2Us divided in two wings).

Despite her damaged bow and greatly reduced speed, Mogami began evasive maneuvers along with Mikuma and received no hits from the Dauntless section.

The following morning, 6 June 1942, Mikuma and Mogami were still heading due west instead of north-west where the combined fleet was converging, hoping to come within the 700 km (430 mi) range of Wake Island's fighter air cover.

The rest of the dive bombers under Short attacked Mikuma from an altitude of 14,000 ft (4,300 m), and caught her as she was coming out of her sharp starboard turn.

The first struck her No.3 turret; the explosion killed many of the officers on the bridge, including the commander of the starboard anti-aircraft batteries, and injured her captain severely enough to render him unconscious.

At 1358, the fire amidships Mikuma reached the torpedoes stored there and triggered a chain of massive secondary explosions, putting to rest the hope of towing the ship out of danger.

Though it wasn't obvious at the time, the bomb hit on the port machinery spaces had also ruptured the ship below the waterline, and she began taking on water.

Arashio and Mogami immediately commenced evasive maneuvers, leaving behind them many of Mikuma's crew in the water who were still making their way to their accompanying ships.

[9][full citation needed] Mogami received a hit near the seaplane deck, which started a fire near the sick bay and killed almost all of the ship's doctors and their orderlies outright.

Realizing the urgency of the situation, Captain Akira Soji, then in command of the detachment, communicated to the Combined Fleet to inform them of the attack, and immediately set course west to vacate the area before more air attacks occurred, leaving most of Mikuma's crew in the water, Mogami and the two destroyers of DesDiv8 sailed away from her, having had time to rescue only 239 of her crew, including her dying captain Sakiyama.

A survivor recalled that Mikuma's port list began increasing rapidly at dusk, and at approximately 1930, she finally turned over on her portside and sank at 29°20′N 173°30′E / 29.333°N 173.500°E / 29.333; 173.500.

Captain Soji later ordered Asashio to reverse course and go back to Mikuma and make every effort to save any of her surviving crews.

[10][full citation needed] However, two of Mikuma's crew would be rescued by USS Trout (SS-202) on 9 June, the only survivors on a life raft that originally held seventeen.