The Roots of Japanese Expansionism in East Asia

Japan’s imperial ambitions toward mainland Asia stretched back centuries before the infamous 1927 Eastern Conference. The seeds were planted during the late 16th century when warlord Toyotomi Hideyoshi, having unified Japan, first articulated dreams of conquering Korea and China. This expansionist mindset became institutionalized following the 1868 Meiji Restoration, as Japan rapidly modernized while simultaneously developing its continental policy focused on Chinese territory.

Over the next seven decades, Japan would launch fourteen foreign military campaigns, with ten specifically targeting China. Victories in the First Sino-Japanese War (1894-1895) and Russo-Japanese War (1904-1905) established Japan as a colonial power with dominant interests in northeast China. By the early 20th century, Japan had transformed into what historians describe as a “military-feudal imperialist” state, increasingly viewing armed conquest as essential to national survival and global standing.

The Eastern Conference and the Tanaka Memorandum

In summer 1927, Prime Minister Tanaka Giichi convened the pivotal Eastern Conference in Tokyo, gathering military leaders and colonial administrators to formalize Japan’s China policy. The resulting document, “Outline of Policy Toward China,” explicitly called for detaching Manchuria and Inner Mongolia from Chinese control as a base for further continental expansion.

The conference’s most notorious outcome was the so-called Tanaka Memorial, allegedly presented to Emperor Hirohito, which declared: “To conquer China, we must first conquer Manchuria and Mongolia. To conquer the world, we must first conquer China.” While historians debate the memorandum’s authenticity, its principles undeniably reflected Japan’s strategic thinking. The Eastern Conference marked a decisive shift toward direct military intervention, with Manchuria identified as the critical first target.

The “Staff Officer Tours” and War Planning

Between 1929 and 1931, Japan’s Kwantung Army – the force stationed in China’s northeast – conducted three systematic reconnaissance missions dubbed “Staff Officer Tours.” These expeditions, led by Colonel Ishiwara Kanji and Lieutenant Colonel Itagaki Seishiro, served dual purposes: assessing Manchuria’s military geography and refining occupation plans.

The first tour (July 1929) focused on northern Manchuria, during which Ishiwara articulated his strategic vision in two key documents. His “Fundamental Plan for Solving the Manchurian Problem” argued that controlling Manchuria represented Japan’s only path to economic survival and future victory in an inevitable US-Japan war. The companion “Kwantung Army Occupation Plan” detailed how Japan would administer the region, including disarming Chinese forces and establishing ethnic-based labor systems.

Subsequent tours in late 1929 (western Liaoning) and 1931 (return to northern Manchuria) tested operational plans for attacking key cities like Harbin and Jinzhou. By 1930, these efforts produced a comprehensive occupation blueprint titled “Research on Administering Occupied Manchuria,” which addressed everything from resource extraction to governance structures.

Creating Casus Belli: The Wanbaoshan and Nakamura Incidents

As military preparations advanced, Japan needed provocations to justify invasion. The Wanbaoshan Incident (July 1931) began as a local dispute between Chinese farmers and Korean immigrants (encouraged by Japanese authorities to settle in Manchuria) over irrigation rights. Japanese consular police intervened on the Koreans’ behalf, then sensationalized reports of Korean casualties sparked anti-Chinese riots in Korea itself, leaving hundreds of Chinese residents dead.

More consequential was the August 1931 Nakamura Affair. Captain Nakamura Shintaro, a Japanese army intelligence officer operating in disguise, was captured and executed by Chinese troops after being discovered conducting military surveys in a restricted border zone. Japanese authorities transformed this legitimate counterespionage operation into a national outrage, with newspapers demanding vengeance and military officials calling it “heaven-sent justification” for invasion.

The Final Countdown to Invasion

By mid-1931, all pieces were in place. The Kwantung Army’s “Manchurian Problem Solution Plan” (March 1931) authorized independent action to overthrow Manchurian warlord Zhang Xueliang. Tokyo’s military leadership simultaneously approved the “Outline for Solving the Manchurian Problem” (June 1931), setting a one-year timetable for invasion.

When the Kwantung Army finally staged the Mukden Incident on September 18, 1931 – fabricating a Chinese attack on Japanese railways – it merely executed plans years in the making. The subsequent occupation unfolded with remarkable precision, following the blueprints developed during the Staff Officer Tours.

Legacy and Historical Significance

Japan’s meticulous preparation for the Manchurian invasion reveals how militarism became institutionalized in its foreign policy. The 1927-1931 period demonstrates how perceived economic needs, racial ideologies, and strategic anxieties combined to make war appear inevitable to Japanese leaders.

Modern scholars view this era as critical for understanding both the Pacific War’s origins and the dynamics of imperial aggression. The systematic nature of Japan’s planning – combining military reconnaissance, political subversion, and propaganda campaigns – established patterns that would characterize 20th-century conflicts. Today, these events remain central to East Asian historical memory and ongoing regional tensions.