The turbines were designed to produce 38,500 shaft horsepower (28,700 kW), which would propel the ships at 37.25 knots (68.99 km/h; 42.87 mph).

[3] In the late 1930s, the ship participated in combat in the Second Sino-Japanese War, covering the landings of Japanese troops in central and southern China.

[6] After taking heavy losses (including Kisaragi and Hayate), the Japanese force withdrew without landing.

[8][page needed] Mochizuki returned on December 23 with the second Wake Island invasion force before sailing back to Kwajalein.

[5] The ship escorted a convoy from Kwajalein to the naval base at Truk in January 1942, where a sponson was installed for a pair of license-built 13.2 mm (0.5 in) Type 93 anti-aircraft machineguns on the forward side of the bridge, and then to Guam.

[9][full citation needed] During the Battle of the Coral Sea from 7–8 May 1942, Mochizuki was assigned to the Operation Mo invasion force for Port Moresby.

On 14–15 October Mochizuki provided cover for the cruisers Kinugasa and Chōkai during a bombardment of Henderson Field.

[10][full citation needed] Throughout November, Mochizuki made numerous “Tokyo Express” troop transport runs to Guadalcanal.

In the remainder of the month, she served as escort to the cruisers Kumano and Suzuya in the Admiralty Islands operations, and landings of troops at Buna and Finschhafen in New Guinea.

After making two Tokyo Express runs from Rabaul to Kolombangara and Rekata Bay in January 1943, Mochizuki returned to Sasebo for repairs.