UPDATED! As promised

The Imperial Japanese Army-Imperial Japanese Navy rivalry wasn't some residual conflict between Prussians and Limeys. After all, the earliest Army advisors were French, anyways! It had much more to do with regional divisions, social divides, bureaucratic infighting, and political armwrestling. The Imperial Japanese Army (IJA) and the Imperial Japanese Navy (Navy) had their own institutional cultures and priorities. These differences lead to intense inter-service friction from formation of the two branches in 1868 up until they were abolished in 1945. As time went on, the rivalry mutated and became more and more toxic. The two factions never really resolved their differences.

It's not that Japan is unique in having Army-Navy tensions. Royal Navy culture and traditions were (and still are) different from British Army culture, just as there were cultural differences between ever other army and navy of the 20th century. Inter-service rivalry caused the United States plenty of problems in WWII, for example, and it such rivalries are still issues modern militaries have to navigate

However, Japanese IJN-IJA rivalries were especially toxic.

The rivalry often crept into domestic politics, causing period of earthshaking political instability in Japan. In 1900 admiral Yamamoto Gombei essentially held the army hostage. With general Katsura Tarō Yamamoto about to become prime minister, Yamamoto gave Katsura his demands. Unless Katsura agreed to increase naval spending, Yamamoto would stop the Navy from appointing a navy minister. Without a full cabinet, Katsura couldn’t form a government, and his prime ministership would be over before it began. In 1901, Katsura finally folded.

In 1912, the Army would do nearly the same thing when Prime Minister Saionji Kinmochi tried to cut defense spending. Katsura was again tapped as prime minister and the Navy tried to pull the same stunt, refusing to appoint a navy minister unless they got some new battleships. Furious, Katsura got the emperor to force the Navy to appoint a minister. The Navy still got the last laugh, though. Katsura’s government collapsed after a no-confidence vote and Katsur’as arch-rvial Yamamoto Gombei became prime minister.

Army-Navy divisions lead both sides to create redundant capabilities. Because the Army dragged its feet in providing troops for amphibious operations, the Navy simply created the own army. In the 1920s, the Navy formed its own Special Naval Landing Forces (Kaigun Tokubetsu Rikusentai). Eventually, the Navy even established SNLF paratrooper units, nevermind that the Army already had airborne units. Meanwhile, the Army was creating its own navy. The Imperial Japanese Army built several sub chasers, submarines, and large transport ships for amphibious operations. It even build its own aircraft carrier, the Akitsu Maru! The air forces of both branches insisted on developing and building their own aircraft, even when it would have been more efficient to standardize on one type – contrast this with the USN and USAAF, which frequently used the same aircraft types (ex. the B-24 and the PB4Y-1 Liberator).

Both sides often withheld crucial information from the others. In the 1930s, the Army (or at least part of the Army) picked a fight with the Soviet Union without telling the Navy. In 1942, the Navy initially concealed the scale of the Midway defeat from the Army, only admitting they’d lost one carrier was lost and a heavy cruiser.

There's a good bit from an interview with historian Edward Drea that illustrates just how poorly the IJA and IJN worked together:

The relations between the Japanese army and navy high commands made American interservice rivalry look like complete agreement. They wouldn’t even share their operational plans. The army was astounded to find that the navy had a full timetable laid out for an attack on Pearl Harbor five months before it happened. Of course, the army didn’t tell the navy what it was doing in China.

... The army always looked north, to fight a war on the continent against the Soviet Union. The navy always looked south, to fight a decisive naval engagement against the United States. Two quite separate strategies.

Where did this inter-service feud come from? How did it get so intense?

It’s difficult to pinpoint a single cause, simply because the nature of the rivalry evolved and expanded over time. As David Evans and Mark Peattie write:

The conflict’s causes—professional hubris, jealousies that arose from old regional antagonism, as well as honest differences in strategic perspective—were multiple and became so intertwined that in tracing the history of the Imperial Japanese Navy, it is difficult to separate them.

Regional rivalries - In the mid and late 1800s, the Army's officer class drew heavily from men from the former Chōshū han (domain) in southern Honshu. Most of these officers were former samurai or the sons of former samurai families. The Navy, by contrast, had a large number of officers from the former Satsuma han in southern Kyushu. Although both domains had cooperated during the 1860s Boshin War that enabled the Meiji Restoration, they had long-standing bad blood that tainted the relationship between the Army and Navy.

This also lead to intra-Army discord. Officers who weren’t from the old Chōshū area seldom got promoted to general rank. Angry at the Chōshū strangehold on promotions, ambitious majors and colonels formed a secret society in the 1920s. The ultranationalistic, militaristic Double Leaf Society (Futabakai) sought to purge “corrupt” senior officers from the army. Eventually, the Army’s officer ranks did diversify somewhat by the late 1920s and 1930s – in part because the growing army had to cast a wider net to get enough senior officers.

As time went on, the Army-Navy split evolved from a inter-regional dispute into a full-fledged intra-national, inter-service disupute. As J. Charles Schencking writes:

The Navy's emergence as a strong elite in Meiji-Taishō Japan contributed to another phenomenon that manifested itself with increasing regularity in early Shōwa Japan: army-navy rivalry. In pre-World War II Japan, that rivalry expanded well beyond clan-based factionalism and institutional outlook; it encompassed appropriations, research, and development, and it fostered conflicting notions concerning the direction and nature of Japanese imperial expansion. Many early naval leaders had previously held positions in the army, both services grew increasingly competitive from the mid- to late 1880s onwards, As each service grew in size and developed its own strategic identity and outlook, rival evolved from a geographically based-competition to one which revolved around matters of greater significance: specifically, matters of military organization and command, imperial expansion, and most important of all, budgets.

Continued...