Japanese nationalism played a pivotal role in shaping the country's foreign policy in the 1930s. Nationalistic fervor, fueled by perceived racial discrimination at the hands of Western powers and a desire to assert Japan as a dominant Asian power, drove Japan's aggressive expansionist policies. Nationalism was also used by the military and government to justify territorial expansions and militarization, painting these actions as necessary for the nation's prestige and security. This nationalist ideology was widespread, permeating through education, media, and popular culture, creating a societal consensus that supported Japan's militaristic and imperialistic ambitions. Thus, nationalism was both a cause and a tool for Japan's expansionist foreign policy.

The Manchurian Incident of 1931 had a profound impact on Sino-Japanese relations. It marked the beginning of direct military conflict between China and Japan, leading to the establishment of the puppet state of Manchukuo by Japan in Chinese territory. This act of aggression significantly heightened tensions and resentment between the two nations. China felt betrayed and violated, leading to a surge in anti-Japanese sentiment among the Chinese population. The incident also set a precedent for further Japanese military ventures in China, culminating in the full-scale invasion in 1937. These events deepened the rift between China and Japan, laying the groundwork for decades of troubled relations.

The signing of the Tripartite Pact in 1940, aligning Japan with Germany and Italy, had significant impacts on Japan's international relations. It marked a decisive shift in Japan's foreign policy from regional Asian concerns to a broader global alignment with the Axis powers. This pact further strained Japan's relations with the Western powers, especially the United States and the British Empire, as it was perceived as a direct threat to their interests in the Asia-Pacific region. The alliance also emboldened Japan's military leaders, who saw the support of powerful European nations as a green light for further expansionist activities. Consequently, the Pact pushed Japan further down the path of confrontation and conflict, ultimately leading to its entry into World War II with the attack on Pearl Harbor in 1941.

Japan's economic conditions in the 1920s and 1930s played a crucial role in its turn towards militarism. The 1920s saw Japan experiencing financial growth, yet it was fragile and heavily reliant on foreign trade and investment. The Great Depression of 1929 severely impacted this economic structure, leading to widespread unemployment and social unrest. The economic downturn undermined the public's confidence in the government's ability to manage the economy, creating a vacuum that the military filled. The military and nationalist groups promoted the idea that expansion into resource-rich areas of Asia could alleviate economic woes, thus linking economic recovery with military expansion, which in turn led to a more aggressive foreign policy.

Japan's withdrawal from the League of Nations in 1933 had significant consequences. It marked Japan's transition from international cooperation to aggressive unilateralism in foreign policy. This withdrawal was a clear indication of Japan's defiance against the international criticism of its actions in Manchuria and its rejection of the global order as represented by the League. Subsequently, Japan pursued its expansionist ambitions in Asia with less restraint, leading to further territorial acquisitions and increased military presence in the region. This move also isolated Japan diplomatically, as it turned away from the Western powers and towards a more nationalistic and militaristic stance, setting the stage for its later alignment with the Axis powers.