There has been speculation that a peace proposal to the Allies was contained on board the I-52 as well, but this is unlikely on two counts: there is no evidence that the Japanese government was interested in peace proposals or negotiated settlements at that stage in the war; and the Japanese kept an open dialogue with their diplomatic attachés via radio and diplomatic voucher through Russia, and had no need for long and uncertain transfer via a submarine bound for a Nazi-controlled area of western Europe.

In addition, 35 to 40 tons of secret documents, drawings, and strategic cargo awaited I-52's return trip to Japan: T-5 acoustic torpedoes, a Jumo 213-A motor used on the long-nosed Focke-Wulf Fw 190D fighter, radar equipment, vacuum tubes, ball bearings, bombsights, chemicals, alloy steel, and optical glass.

[2][5] Yanagi missions were enabled under the Axis Powers' Tripartite Pact to provide for an exchange of strategic materials and manufactured goods between Germany, Italy and Japan.

She also carried 14 passengers, primarily Japanese technicians, who were to study German technology in anti-aircraft guns and engines for torpedo boats.

On 6 June 1944, the Japanese naval attaché in Berlin, Rear Admiral Kojima Hideo, signaled the submarine that the Allies had landed in Normandy, thus threatening her eventual destination of Lorient on the coast of France.

[7] On the night of 22 June 1944 about 850 nautical miles (1,574 km) west of the Cape Verde Islands off the coast of Africa, I-52 rendezvoused with U-530, a Type IXC/40 U-boat commanded by Kapitänleutnant Kurt Lange.

The five destroyer escorts were: Arriving in the area of the meeting on the evening of 23 June, the carrier began launching flights of Avengers at around 23:00 GMT to search for the submarines.

The Mark 24, code-name "Fido" and designated a "mine" for secrecy, was actually the first Allied acoustic torpedo, developed by the Harvard Underwater Sound Lab, which homed in on noises made by the submarine.

However, as Taylor's patrol ended, he was relieved by Lieutenant Junior Grade William "Flash" Gordon, accompanied by civilian underwater sound expert Price Fish.

Captain Vosseller ordered a second attack; Gordon checked with Taylor about the exact position of the sonobuoy and dropped another "Fido" torpedo where he believed the submarine to be.

Next morning, USS Janssen reached the site (15°16′N 39°55′W / 15.267°N 39.917°W / 15.267; -39.917) and found flotsam: a ton of raw rubber, a piece of silk, and human flesh.

The sonobuoy recording of the last few moments of I-52's sound still survives in the US National Archives in Washington D.C. in the form of two thin-film canisters marked "Gordon wire No.

On the wire and vinyl recordings, Lieutenant Gordon can be heard talking to his crew, along with the sound of a torpedo exploding, and metal twisting.

[10] Subsequent to the discovery of the wreck (see below), analysts at the Johns Hopkins University Applied Physics Laboratory, experts in analyzing modern submarine sounds, studied these recordings and concluded that the I-52 was sunk by Taylor.

Very shortly afterwards, however, in the spring of 1995, Paul Tidwell, working with the ocean exploration company Meridian Sciences, Inc. (later renamed Nauticos Corp.) located the wreck 17,000 feet (5,200 metres; 3.2 miles) deep, mostly upright.

Meridian's analysts used historical ship logs from the U.S. task force as well as from the German U-boat to reconstruct the events of the battle and correct navigation errors using a process called "re-navigation," or RENAV.

Tidwell worked on the proper procedures with the Japanese government and received the approval of the war graves authorities in Japan.

The plan was to recover the entire conning tower, diplomatic pouches, gold, coding equipment, (Japanese and German) and more.