Originally built as the submarine support ship Tsurugizaki (Japanese: 剣埼, "Sword Cape") in the late 1930s, she was converted before the Pacific War into an aircraft carrier and renamed.

Shōhō and her sister Zuihō were designed to be easily modified as an oil tanker, submarine tender, or aircraft carrier as needed.

As part of her conversion, her original diesel engines, which had given her a top speed of 29 knots (54 km/h; 33 mph), were replaced by a pair of destroyer-type geared steam turbine sets with a total of 52,000 shaft horsepower (39,000 kW), each driving one propeller.

The boilers exhausted through a single downturned starboard funnel and she carried 2,642 tonnes (2,600 long tons) of fuel oil, giving her a range of 7,800 nautical miles (14,400 km; 9,000 mi) at a speed of 18 knots (33 km/h; 21 mph).

[4] The ship's primary armament consisted of eight 40-caliber 12.7 cm Type 89 anti-aircraft (AA) guns in twin mounts on sponsons along the sides of the hull.

Shōhō was also initially equipped with four twin 25 mm Type 96 light AA guns, also in sponsons along the sides of the hull.

Covering the other elements of Operation MO was the Striking Force that consisted of the fleet carriers Shōkaku and Zuikaku.

US Army Air Forces (USAAF) aircraft spotted Shōhō[Note 1] southwest of Bougainville Island on 5 May, but she was too far north to be attacked by the American carriers, which were refueling.

[11] That day, Rear Admiral Frank Jack Fletcher received Magic intelligence that placed the three Japanese carriers known to be involved in Operation MO near Bougainville, and predicted 10 May as the date of the invasion.

Based on this information, Fletcher planned to complete refuelling his ships on 6 May and move closer to the eastern tip of New Guinea to be in a position to locate and attack Japanese forces on 7 May.

The Japanese, however, were unwilling or unable to launch air strikes in poor weather or without updated spot reports.

[14] The Japanese were the first to spot the Americans when one aircraft found the oiler Neosho escorted by the destroyer Sims at 0722, south of the Strike Force.

[15] American reconnaissance aircraft reported two Japanese heavy cruisers northeast of Misima Island in the Louisiade Archipelago off the eastern tip of New Guinea at 07:35 and two carriers at 08:15.

These penetrated the ship's flight deck and burst inside her hangars, setting the fuelled and armed aircraft there on fire.

Yorktown's aircraft trailed those from Lexington, and the former's Dauntlesses began their attacks at 11:25, hitting Shōhō with another eleven 1,000-pound bombs by Japanese accounts and the carrier came to a complete stop.