In a sense, it was the three reasons you listed - nationalism, military training and government propaganda - as one, with mutually supporting links between all three, that contributed to the fanatical approach of Japanese soldiers in the 1930s and 1940s. I will mostly be covering the 1937-1941 period - but the same ideas are applicable for the 1941-1945 period as well.

The reason why an attitude of ‘death or dishonour’ was emphasised in the Imperial Japanese armed forces can be traced back to Japanese tactical doctrine. Uniquely among modern twentieth century armies after WWI, the Japanese high command remained adherents of bayonet warfare. They believed that cold steel could triumph over the bullet if the troops had high morale and élan. Hence, an aggressive offensive doctrine was established by the Imperial Japanese Army (IJA), by which frontal forces pinned down the main body of the enemy to allow for a decisive bayonet charge on both flanks. In the Russo-Japanese War, as well as the Siege of Tsingtao during WWI, both the Russians and Germans were horrified by the number of casualties the Japanese were willing to take to overrun a position. Although army reforms in the inter-war years showed that high command was aware of the lethality of improved firearms, as the standard spacing of a squad was widened while the recommended distance for a bayonet charge was shortened, tactical manuals actually showed a redoubled emphasis on ‘spirit’ and élan for aggressive maneuvers. This focus on military morale can be seen in both military training and propaganda.

Growing up, a conscript would be exposed to a highly militaristic society. Nationalistic propaganda became prevalent in Japan during the 1930s, which glorified both the military and the emperor. The Ministry of Education published a fourth and fifth edition of an ethics textbook made compulsory for school children which was highly militaristic and nationalistic. Textbooks of other subjects also contained military terms and examples. In the assembly before teaching commenced, students had to bow to the flag and in the direction of the Imperial Palace. In major cities, citizens were encouraged to line up in rows, observe a minute’s silence, bow, and shout 'Banzai' during Army Day and Navy Day, which were both established as national holidays. The Japanese government also utilised radios and other media to instil militaristic attitudes in the population. The intense propaganda efforts were so successful that, when the Second Sino-Japanese War started, even the government itself was surprised by the degree of support it received from the population and was forced to expand the war due to public pressure for a greater war effort.

When conscripts entered military training, harsh military discipline enforced ideas of sacrifice for the Emperor and the nation. Every morning before the start of their training, soldiers were required to bow towards the direction of the Imperial Palace. Soldiers had to memorise the Imperial Rescript to Soldiers and Sailors, which established a personal bond between the military and the Emperor. The precept of the Rescript particularly highlights the attitude desired by the Japanese military: ‘The soldier and sailor should consider loyalty their essential duty. Who that is born in this land can be wanting in the spirit of grateful service to it? No soldier or sailor, especially, can be considered efficient unless this spirit be strong within him...with single heart fulfil your essential duty of loyalty, and bear in mind that duty is weightier than a mountain, while death is lighter than a feather. Never by failing in moral principle fall into disgrace an bring dishonour upon your name.’ To train up conscripts' ‘spirit’ and discipline, military training resorted to abuse and beatings. An example would be ordering a recruit to stand at attention, which the recruit would do so until he collapsed. After that, he would receive a beating for ‘not standing at attention’. It was common for officers to beat their men while explaining why they were being beat. Equipment checks were prime opportunities for officers to administer even more beatings, as the equipment was seen as given by the emperor himself. Most recruits bore the beatings with a stoic, fatalistic attitude - shikata ga nai (it can’t be helped). The emphasis of allegiance to the Emperor and military discipline and obedience, which was a natural progression from childhood education, created a soldier who was willing to die for a cause.

Before leaving for the front, soldiers would go through a carefully orchestrated process of sending off that in most cases would be greatly inspiring. A sending-off party, often organised and attended by the whole village, could induce strong emotions in the draftees as they were struck with a sense of responsibility. Umeda Fusao from Kitsuka wrote in his diary that ‘I developed a distinct feeling of warmth growing inside as I was being sent off with a chorus of war songs and the shouting of banzai three times.’ Good luck flags containing messages from relatives, neighbours, friends, and co-workers would be ceremoniously handed over to the soldier. As soldiers departed to the front, people gathered along the railroads and gave offerings to the soldiers. The crowds would chant ‘Banzai!’ while elementary school students waved small Japanese flags. It was often an unforgettable experience for the soldiers, and served as encouragement before the reckoning of the battlefield. Hiraide Kazumoto’s emotions during his departure in August 1937 is similar to other diary accounts of the departures: ‘I was the most touched by the sight of an elementary school student vigorously waving a small Hinomaru (Japanese flag) back and forth. That I would put my life on the line to fight gave me a certain kind of pleasure and I was flooded in the joy I felt having been born male.’

However, the Japanese soldier’s conviction and spirit was often impacted by their actual experience of combat. In the Second Sino-Japanese War, as hopes of a quick victory were dashed, Japanese frontline morale dropped significantly. No longer were troops willing to commit to suicidal charges - as a form of passive resistance, soldiers held on to the ankles of officers as they tried to lead forces forward on a charge that the rank-and-line believed to be foolhardy. In more extreme cases, officers who were deemed too fanatical were shoot at in the dark by their own subordinates. In many cases, the human instinct to survive and go home trumped the conscripts’ military education. A 1939 IJA Medical Corps report on the 23rd Infantry Division, which fought against the Soviets at Khalkin Gol and suffered seventy percent casualties, is particularly illuminating. Before combat, troop morale was very high and soldiers believed the Soviets would be easily routed. Most troops had confidence in their equipment and tactics and had an aggressive mindset. However, after the first contact with the enemy, troop morale plummeted as they realised they had been outfought, resulting in group disorientation, breakdown in unit cohesion and in some cases unauthorised withdrawal. In most cases, Japanese soldiers were not mindless robots who carry out orders without regard to their own safety as often depicted in Western media. On the battlefield, many of them were no different from the Chinese, British, Indian, or American troops they faced.

Sources:

Yoshimi Yoshiaki, 'The Second Sino-Japanese War and national mobilization: the issue of rallying soldiers and personal experiences of the battlefield', Japan Forum 24 (2012), 119–130.

The Battle for China: Essays on the Military History of the Sino-Japanese War of 1937-1945, ed. by Mark Peattie, Edward Drea and Hans van de Ven, Stanford, Calif.: Stanford University Press, 2011.

Samuel Hideo Yamashita, Learning How to Die.” Daily Life in Wartime Japan, 1940-1945, Lawrence, Kansas: University Press of Kansas, 2015.

Barak Kushner, The Thought War: Japanese Imperial Propaganda, Honolulu: University of Hawai'i Press, 2006.