The Italian and Japanese exchanges of information and visits were part of a larger effort put in place by both navies during 1938. Through the Italian naval attaché in Tōkyō they discussed the idea of a ‘neutrality agreement’.

If one of the two powers went to war with Great Britain, this would require the other to mobilize its fleet to block part of the Royal Navy in the Mediterranean or at Singapore in order to ease its partner’s situation. It would also provide for active cooperation in case both countries were at war. According to both the Italian and the Japanese documentation, Ferretti concluded that the agreement was not signed because both sides were still in doubt about their future foreign policy.^37^

Uncertainties about their naval planning on the part of all three future Tripartite powers were certainly a factor hampering early [Fascist] attempts to search for [Imperial] cooperation. At this stage the […] Kriegsmarine was concentrating its plans on an Atlantic war against British communications, and the Japanese plans were subject to the swings of Imperial foreign policy, divided between the possibilities of southern or northern expansion. Plans and studies for an Anglo‐Japanese war were not developed until 1938.^38^

Nevertheless, ever since 1935 the Regia Marina had taken war with Great Britain as the cornerstone of its preparations. Much more important in stopping [Fascist] attempts to develop active naval cooperation with [the Empire of] Japan were the difficulties inherent in building the forces necessary to operate in the Indian Ocean.

In 1937, [Fascist] plans called for the deployment in East Africa of a fleet of three cruisers, four flotilla leaders, four destroyers, eight torpedo boats, eight Mas boats and 12 submarines to strike at British communications in the Indian Ocean.^39^

The possibility of cruiser warfare was particularly connected to potential [Imperial] cooperation. Indeed, during the Friedrichshafen meeting (20–1 June 1939), the first joint talks between the [Kriegsmarine] and [Regia Marina] staffs, the commander‐in‐chief of the [Kriegsmarine], Erich Raeder, emphasized that having [Fascist] bases in East Africa would allow the possible deployment of commerce raiders from the Indian Ocean up to the coasts of [Imperial] Japan.^40^

However, the reality turned out to be very different. The [Regia Marina] had to scrap the cruiser programme for the East African bases due to the lack of raw materials, and in 1940 there were only eight submarines in Massowah. [Fascist] Italy’s lack of adequate naval resources hampered naval cooperation with [Imperial] Japan much more than did [Rome’s] indecisiveness about foreign policy.

In 1939 Rome declared itself ready to sign a military pact with Berlin and Tōkyō and conduct joint naval planning to coordinate submarine operations in the Atlantic and Indian Oceans. However, talks went ahead only with the [Third Reich], leading to the signing of the Pact of Steel on 22 May 1939.^41^ As a result, when Fascist Italy [officially] entered the Second World War in June 1940 its expectations of [Imperial] support were reduced to the supply of fuel, rice, and rubber.^42^

In the end, the first phase of naval relations between Fascist Italy and Imperial Japan was a false start. Both powers perceived the other as a potential ally, the [Fascists] in particular acknowledging that facing Great Britain required at least a degree of worldwide perspective involving [Imperial] Japan in their planning for war in the Indian Ocean, but were unable to translate talks into active cooperation.

[…]

Despite [the Third Reich’s] help, the convoys to North Africa absorbed all the Regia Marina’s resources, blocking any attempts to threaten the British position in the eastern Mediterranean and at Suez.^44^ As far as relations with the [Imperial Japanese Navy] were concerned, the most important Italian defeat was the fall of the last [Regia Marina] base on the Red Sea in June 1941, which left the possibility of future cooperation in the Indian Ocean dependent on [Imperial] logistical support.^45^

[…]

The possibility of establishing a proper flow of information was limited by the difficulty of establishing ciphered transmission between [Fascist] Italy and the Far East, making both sides dependent on the [Third Reich] as intermediaries.^52^ Moreover, the Italian cryptographic system was already interlinked with the [Third Reich’s], making it impossible for Italy to act autonomously.^53^ This limited the exchange of intelligence, which could only be provided directly or via diplomatic couriers.

Nevertheless, during the next two years the Italians were willing to share intelligence directly with the [Empire of Japan] where possible. Thus, in February 1942 the [Imperial] Japanese obtained from Rome copies of the Royal Navy’s signal book and fleet tactical instructions found by the [Fascists] in the wreck of the destroyer HMS Mohawk, sunk in the Mediterranean in April 1941.^54^

The attempts at technical cooperation were less effective. In 1939, at the request of the Regia Marina, the Pignone factory in Florence, producer of equipment for underwater mines, forbade [Imperial] officers from visiting its plants.^55^ The same attitude applied when it came to the sale of the Equilibratore Rovetto. [Imperial] attempts to buy samples were not allowed and when, in January 1940, the [Imperial] naval attaché proposed starting licensed production, the Regia Marina rejected his requests.^56^

Similar restrictions were in effect in the following years as the [Fascists] preferred to maintain the ‘secrecy’ of their armaments, despite the fact that the [Imperial] Japanese were not seeking state‐of‐the‐art weapons. Thus in 1941, after the signing of the Tripartite Pact, the Regia Marina blocked a[n] [Imperial] attempt to acquire underwater mines, arguing that it was possible only to offer ‘obsolete mines […] based on principles for which the preservation of secrecy is not an issue’.^57^

The [Fascists’] attitude is explained by their assumption that Italian technology was superior. In 1941, the Regia Marina regarded itself as being ahead of the IJN in many fields: acoustics, submarines, electrical metallurgy, firing systems and range finders. This also explains the Regia Marina’s lack of interest in acquiring [Imperial] technology.^58^

According to the [Imperial] naval attaché in Rome, Captain Toyo Mitsunobu, the Regia Marina’s behaviour regarding the IJN’s technological capacity was dictated by racial stereotypes: from the [Fascist] point of view, the Japanese were only interested in the reverse engineering of ‘superior’ [Fascist] technology.^59^

In 1942, with the [Eastern Axis’s] victories, [Fascist] references to their superior technology disappeared from reports, but the ban on military exports was still active in 1943 — indicating the persistence of the [Fascist] sense of superiority in this regard.

(Emphasis added.)

As we can see, although there were some minor achievements, collaboration between the Regia Marina and the Imperial Japanese Navy was for the most part unfruitful. Reasons for this include (but are unlimited to) the want of naval bases, the want of materials, limited communications, excessive secrecy, and white supremacist arrogance. It was hardly for a lack of trying. The Axis certainly would have lasted longer without these obstacles, but it probably would have still lost the war.