[3] That day, the 6th Fleet's commander, Vice Admiral Mitsumi Shimizu, held a meeting with the commanding officers of the submarines of Submarine Squadron 3 aboard his flagship, the light cruiser Katori, which was anchored in Saeki Bay on the coast of Kyushu , and his chief of staff briefed them on plans for Operation Z, the upcoming surprise attack on Pearl Harbor in Hawaii.

[3] After she arrived at Yokosuka, Rear Admiral Chimaki Kono came aboard I-8 and relieved Miwa as squadron commander, and I-8 put back to sea on 26 April 1942 and again set course for Kwajalein.

[2] Later in October, I-8 put to sea again for another patrol,[2] during which her Watanabe E9W1 (Allied reporting name "Slim") floatplane reconnoitered the harbors at Port Vila and Havannah on Efate in the New Hebrides on 2 November 1942.

[3] Norita's crew and Nishihara brought the number of men aboard I-8 for the voyage to 160, creating very cramped conditions aggravated by the amount of cargo on board.

[3][6] On 21 July 1943, I-8 entered the Atlantic Ocean 300 nautical miles (560 km; 350 mi) south of the Cape of Good Hope on the southern tip of Africa.

[3] Over the next ten days she encountered fierce storms which damaged her upper deck and aircraft hangar and was rarely able to make more than 5 knots (9.3 km/h; 5.8 mph).

[3] On 20 August, she rendezvoused with the German submarine U-161 — under the command of Korvettenkapitän Albrecht Achilles — in the Atlantic Ocean south of the Azores, and an Oberleutnant zur See and two petty officers transferred from U-161 to I-8 to install a radar detector — either a FuMB 1 Metox 600A[citation needed] or a FuMB 9 Wanze,[3] according to different sources — on her bridge,[3] which made I-8 the first Japanese submarine with a radar detector.

[3] I-8′s crew presented U-161 with a four-gallon tank of coffee, and the two submarines parted company, with the three Germans remaining aboard I-8 to guide her into port in German-occupied France.

[3] After she entered the Bay of Biscay on 29 August 1943, the Luftwaffe sent Junkers Ju 88 aircraft[3] of Kampfgeschwader 40[citation needed] to provide air cover.

[7] For her return voyage, I-8 loaded a cargo that included German equipment, including machine guns, bomb sights for horizontal bombers and dive bombers, quad 20 mm anti-aircraft guns, anti-aircraft gunsights, a Daimler-Benz MB 501 20-cylinder diesel torpedo boat engine for German S-boats (known to the Allies as "E-boats"), marine chronometers, radars, sonar equipment, electric torpedoes, and precious metals,[3][7] as well as penicillin.

[3] By November 1943 she had reached the Indian Ocean, where she affixed the hinomaru national identification marking to her conning tower just as a Japanese plane buzzed her, possibly avoiding a mistaken attack by the aircraft.

3 hold and wrecking the winches and derricks around it, knocking down her main and emergency aerials,[12] and jamming her rudder hard to port, forcing her to steam in circles.

[14] The gun ceased fire at 06:00[14] and its crew abandoned ship just before Tsijalak rolled onto her beam ends and sank by the stern 500 nautical miles (930 km; 580 mi) south of Colombo at 02°30′S 078°40′E / 2.500°S 78.667°E / -2.500; 78.667 (SS Tjisalak).

[17] I-8′s crew forced all of the survivors other than the seven they had taken below to squat on deck, threatened them with submachine guns, rifles, and swords, and searched them roughly, confiscating anything of monetary value.

[8][17] Tied together in twos, the European and Chinese crew members were taken two-by-two aft of I-8′s conning tower, where they were slashed with swords and beaten with monkey wrenches and sledgehammers before the Japanese shot them and kicked them overboard.

[19] Those who jumped overboard were shot in the water,[3][18] and at least three of I-8′s crew sat comfortably in chairs on deck and laughed while firing rifles at men struggling in the sea.

[3][8][23] On 30 March 1944, I-8′s Watanabe E9W1 (Allied reporting name "Slim") floatplane sighted the British 6,589-gross register ton armed merchant ship SS City of Adelaide in the Indian Ocean southeast of Diego Garcia in the Chagos Archipelago during a reconnaissance flight.

[2][3] The plane vectored I-8 to intercept City of Adelaide — which was steaming independently in ballast from Karachi in British India to Fremantle, Australia — then returned to I-8.

[2][3] At 06:07 on 11 April 1944, a Japanese submarine — apparently I-8 — fired four torpedoes about four minutes apart at the American armed T2 tanker SS Yamhill in the Indian Ocean at 03°31′N 067°07′E / 3.517°N 67.117°E / 3.517; 67.117.

[2][3][25] Jean Nicolet had departed San Pedro, California, on 12 May 1944 bound for Calcutta, India via Fremantle, Australia, and Colombo, Ceylon,[25] with 69 crew and United States Navy Armed Guard personnel and 30 United States Army passengers aboard[7] — although one source claims that a toal of 100, rather than 99, men were on board[25] — and carrying a U.S. Army cargo of heavy machinery, steel plates, and landing craft in her holds and mooring pontoons and unassembled landing barges on her deck.

[26] Advised on 27 June 1944 to alter course to the west to avoid the area where I-8 had sunk Nellore 500 nautical miles (930 km; 580 mi) to the north that day,[26] Jean Nicolet′s′ crew sighted what her captain thought was the smoke of an Allied Victory ship on her port quarter on the morning of 2 July 1944 and watched it overtake Jean Nicolet during the day, reaching a point off her starboard bow at sunset.

[24] Shortly after the torpedoes hit, Jean Nicolet transmitted a distress signal[28] and all on board abandoned ship in her four lifeboats and two life rafts.

[30] I-8′s crew then riddled the empty lifeboat with automatic weapons fire,[31] confiscated the survivors′ lifejackets, shoes, and anything of value they had, then bound them and forced them to sit on I-8′s deck.

[3][32] After the Japanese searched the survivors, took their lifejackets, bound them, questioned them, and forced them all to sit on I-8′s forward deck, I-8 got underway and circled the area while her crew destroyed all the lifeboats and life rafts with automatic weapons fire.

[35] One by one over the next several hours, the rest of the survivors then also were led aft of the conning tower, forced to run a gauntlet of clubs, pipes, bayonets, knives, and swords,[36][35] and then shoved overboard to drown.

[36][37] With 30 bound survivors still on deck and awaiting their turn to run the gauntlet,[37] I-8 detected an incoming aircraft on radar[3][38] and abruptly crash-dived, plunging them into the ocean to drown as the submarine submerged beneath them.

[3] One source asserts that I-8′s crew took five prisoners-of-war from Jean Nicolet to Japan, where one of them, Francis J. O'Gara, was found alive in a prisoner-of-war camp after World War II.

[3] I-8 departed Penang later in September 1944[2] and arrived on 9 October 1944 at Yokosuka,[2][3] where she underwent a refit, repairs, and modifications, including the removal of her hangar and aircraft catapult and their replacement with fittings for kaiten manned suicide attack torpedoes.

[3] At 18:05 on 28 March 1945, she transmitted a message reporting that she had sighted two Allied transports and four destroyers 110 nautical miles (200 km; 130 mi) from Naha, bearing 150 degrees.

On 31 March 1945, the U.S. Navy destroyer USS Stockton (DD-646) detected a surface target on radar while screening a task group off the Kerama Islands.