Part 1 of 2

Sorry for the late response, but I hope I can share some insight on Japanese army doctrine in the Imperial period.

The core doctrine of the Imperial Japanese Army (IJA) could best be described as "spiritual superiority", or--as the IJA would more commonly put it--the "intangibles" of war, in terms of fighting spirit. The IJA recognised that in any future war with any of its future enemies, Japanese armies would likely find themselves in a position of significant material inferiority, likely outnumbered and outgunned by their rivals. In order to this disadvantage, the IJA turned to the fighting spirit of its soldiers, believing that spiritual superiority would enable their soldiers to overcome the material superiority of their rivals. On an operational and tactical level, this would manifest in aggressive action on all levels. Unfortunately, the IJA lacked much in the way of strategic planning, and so was ultimately reliant on a hope that early victories would produce a fait accompli, which their enemies would lack the political will to overcome. To the Western mind, where war is often viewed in highly material terms, the IJAs reliance on intangible factors like fighting spirit can seem like little more than wishful thinking at best or mere mysticism at worst. Yet, the focus on fighting spirit was heavily guided by the IJA's experience in war, as well as serving as one of the few ways it could hope to overcome the advantages held by its likely opponents, nor was it a belief unique to the IJA.

When examining the development of the IJA's focus on intangible factors it is best to start from the beginning, with the Imperial Army's first major test in combat: the Satsuma Rebellion of 1877. Led by one of the architects of the overthrow of the Shogunate, Saigō Takamori, the Satsuma Rebellion saw large number of disaffected samurai from the Satsuma Domain in southern Kyushu. During the rebellion, the relatively new IJA boasted an impressive material superiority over the rebellious samurai, with substantially more and modern artillery and small arms. Despite this, the IJA found itself very disappointed in the performance of its new soldiers, many of whom were conscripted peasants, finding that for all their superior equipment, the fighting spirit and morale of the samurai enabled the rebels to field qualitatively superior forces. The Army was forced to enlist large numbers of former samurai both to replace losses, and to serve as shock troops on the front lines. From the Satsuma Rebellion, the IJA took the lesson that there was some form of intangible quality amongst the samurai that had enabled their superior combat performance, and that these intangibles--usually seen as 'morale' or 'fighting spirit'--were the decisive factors in the war. The Army thus sought to inculcate those same intangible factors into its forces, seeing them as more important the superior firepower or numbers in overcoming potential enemies.

This belief in the importance of spiritual superiority and intangible factors would underlie much of the IJAs future development. To quote Edward Drea:

Over time a reliance on intangible qualities came to mean a willingness to fight to the death regardless of the situation. Once that concept gained acceptance, death in battle became the standard by which to measure fighting spirit. No matter how bravely enlisted troops acquitted themselves in battle, their very survival could be and was interpreted by staff officers as indicative of a lack of fighting spirit that adversely affected overall performance.

Self-sacrifice became the measuring stick by which superior fighting spirit could be measured. Troops who were willing to die in the attempt to carry out their objectives (successfully or not) were lionised within both the Army, and in wider popular culture. During the First Sino-Japanese War, the Army saw its reliance on intangibles as justified, although the army of the late Qing was hardly the most effective fighting force in the world and the Navy's defeat of the Beiyang Fleet off the Yalu River gave the Japanese control of the Yellow Sea. Victory against the Russian Empire in the Russo-Japanese War also served to reinforce the IJA's belief in the supremacy of its focus on intangibles over Russian superiority in material an numbers. During the war, Japanese infantry had attacked directly into Russian fortifications in the Liaodong Peninsula, taking massive losses but ultimately succeeded in forcing the Russians to retreat. The Army praised the soldiers who had died in these "human-bullet attacks", holding them up as ideals of Japanese self-sacrifice and proof that the superior fighting spirit of the Japanese soldier could overcome machine guns. Outside of the Siege of Port Arthur, in the more open ground of Manchuria, the Japanese sought to advance rapidly, seeking to envelop and destroy Russian field armies, before reinforcements could arrive from European Russia. In this they were unsuccessful, and while Japanese attacks managed to take Mukden (modern Shenyang), the army was exhausted and unable to push onward. Despite this, and with the added influence of the Navy's great victory at Tsushima, the Tsar decided to negotiate peace, as the repeated defeats and the general unpopularity of the war made sustaining it impossible.