[Note 1] Sōryū's aircraft were employed in operations during the Second Sino-Japanese War in the late 1930s and supported the Japanese invasion of French Indochina in mid-1940.

During the first months of the Pacific War, she took part in the attack on Pearl Harbor, the Battle of Wake Island, and supported the conquest of the Dutch East Indies.

In April, Sōryū's aircraft helped sink two British heavy cruisers and several merchant ships during the Indian Ocean raid.

The loss of Sōryū and three other IJN carriers at Midway was a crucial strategic defeat for Japan and contributed significantly to the Allies' ultimate victory in the Pacific.

The ship's power and slim, cruiser-type hull, with a length-to-beam ratio of 10:1, gave her a speed of 34.5 knots (63.9 km/h; 39.7 mph)[6] and made her the fastest carrier in the world at the time of her commissioning.

[10] The gun was the standard Japanese light AA weapon during World War II, but it suffered from severe design shortcomings that rendered it largely ineffective.

[13] To save weight Sōryū was minimally armored; her waterline belt of 41 millimeters (1.6 in) of Ducol steel only protected the machinery spaces and the magazines.

From a position 230 nautical miles (430 km; 260 mi) north of Oahu, Sōryū and the other five carriers launched two waves of aircraft on the morning of 8 December 1941 (Japan time).

One torpedo passed underneath Oglala and struck Helena in one of her engine rooms; the other pilot rejected these targets and attacked the battleship California.

[20] The two carriers reached the vicinity of the island on 21 December and launched twenty-nine D3As and two B5Ns, escorted by eighteen Zeros, to attack ground targets.

Several hours later, nine of Sōryū's D3As located and bombed an American supply ship of 3,200 gross register tons (GRT), Don Isidro, hitting her five times but failing to sink her.

[29] Sōryū and the other carriers arrived at Staring Bay on Celebes Island on 21 February to resupply and rest before departing four days later to support the invasion of Java.

The four carriers launched an airstrike of 180 aircraft against Tjilatjep on 5 March, sinking five small ships, damaging another nine badly enough that they had to be scuttled, and set the town on fire.

Two days later they attacked Christmas Island before returning to Staring Bay on 11 March[20] to resupply and train for the impending Indian Ocean raid.

This raid was intended to secure newly conquered Burma, Malaya, and the Dutch East Indies against Allied attack by destroying base facilities and forces in the eastern Indian Ocean.

[30] On 26 March 1942, the five carriers of the First Air Fleet departed from Staring Bay; they were spotted by a Catalina about 350 nautical miles (650 km; 400 mi) southeast of Ceylon on the morning of 4 April.

Meanwhile, a floatplane from the battleship Haruna spotted the small aircraft carrier Hermes, escorted by the Australian destroyer Vampire, and every available D3A was launched to attack the ships.

They sank the oil tanker British Sergeant and the Norwegian cargo ship Norviken before they were attacked by eight Fulmars of 803 and 806 Naval Air Squadrons.

While this was going on, Akagi narrowly escaped damage when nine British Bristol Blenheim bombers from Ceylon penetrated the CAP and dropped their bombs from 11,000 feet (3,400 m).

After launching the D3As that sank Hermes and the other ships, the First Air Fleet reversed course and headed southeast for the Malacca Strait before recovering their aircraft; they then proceeded to Japan.

[32] On 19 April, while transiting the Bashi Straits between Taiwan and Luzon en route to Japan, Akagi, Sōryū, and Hiryū were sent in pursuit of the American carriers Hornet and Enterprise, which had launched the Doolittle Raid against Tokyo.

[36] With the fleet positioned 250 nautical miles (460 km; 290 mi) northwest of Midway at dawn (04:45 local time) on 4 June 1942, Sōryū's part in the 108-plane combined air raid was a strike on the airfield on Eastern Island with eighteen torpedo bombers escorted by nine Zeros.

The air group suffered heavily during the attack; a single B5N was shot down by fighters, two more were forced to ditch on the return (both crews rescued), and five (including one that landed aboard Hiryu) were damaged beyond repair.

[37] The Japanese did not know that the US Navy had discovered their MI plan by breaking their cipher, and had prepared an ambush using its three available carriers, positioned northeast of Midway.

The thirty CAP Zeros in the air at this time, including the six from Sōryū, immediately attacked the American airplanes, shooting down five of the Avengers and two of the B-26s.

The process normally took about an hour and a half; more time would be required to bring the aircraft up to the flight deck, and to warm up and launch the strike group.

The high altitude of the B-17s gave the Japanese captains enough time to anticipate where the bombs would land and successfully maneuver their ships out of the impact area.

[43] The CAP defeated the next American air strike from Midway, shooting down three of the eleven Vought SB2U Vindicator dive bombers from VMSB-241, which attacked the battleship Haruna unsuccessfully, starting at around 08:30.

The hangars contained armed and fueled aircraft preparing for the upcoming strike, resulting in secondary explosions and rupturing the steam pipes in the boiler rooms.

Sōryū was still afloat and showed no signs of beginning to sink by early evening, so Isokaze was ordered to scuttle her with torpedoes so as to allow the destroyers to be used for possible operations that night.