Japan's expansionist policies in Southeast Asia and the Pacific were driven by several objectives. Primarily, Japan sought to secure vital natural resources, such as oil, rubber, and minerals, which were crucial for its industrial and military needs. Southeast Asia, rich in these resources, became a key target for Japanese expansion. Additionally, Japan aimed to establish a strategic buffer zone to protect its home islands and extend its defensive perimeter. The concept of the Greater East Asia Co-Prosperity Sphere was also a driving force, with Japan intending to create an economic and military bloc in Asia, free from Western influence. This expansion was part of Japan's broader goal of establishing itself as the dominant power in the region, challenging Western colonial powers and asserting its authority over Asia.

The economic sanctions imposed by the United States, particularly the oil embargo in 1941, significantly influenced Japan's decision to enter World War II. These sanctions were a response to Japan's aggressive expansion in Asia, especially in China and Indochina. The embargo threatened Japan's military operations and industrial growth, as it was heavily reliant on American oil supplies. Faced with the prospect of economic strangulation and the depletion of existing oil reserves, the Japanese leadership saw war with the United States as inevitable. The decision to attack Pearl Harbor was a strategic move to pre-emptively weaken U.S. military capacity in the Pacific, allowing Japan to secure the resources it needed for its war efforts and territorial expansion. The sanctions thus played a pivotal role in escalating the conflict, forcing Japan into a position where it felt compelled to take drastic military action.

Japan's actions in China played a crucial role in escalating the regional conflict into the broader context of World War II. The full-scale invasion of China in 1937, marked by events like the Nanjing Massacre, attracted international condemnation and heightened tensions with Western powers, particularly the United States. Japan's aggressive stance and refusal to withdraw from China led to a deterioration of diplomatic relations and eventually economic sanctions from the U.S. and its allies. These actions directly contributed to Japan's decision to expand its military operations into Southeast Asia and the Pacific, seeking resources to continue its war efforts. The attack on Pearl Harbor in 1941 was a direct consequence of these escalating tensions, leading to Japan's formal entry into World War II and the expansion of the conflict into a global war. Japan's relentless pursuit of its expansionist goals in China thus set the stage for its involvement in the global conflict.

Japanese nationalism played a critical role in shaping the country's foreign policy during the 1930s. The concept of national superiority, coupled with historical grievances against Western powers, fueled a desire for territorial expansion and dominance in Asia. Nationalistic education and propaganda promoted the idea of Japan as a liberator of Asia from Western colonialism, creating widespread public support for expansionist policies. This nationalism was intricately linked to the military's goals, with the belief that Japan was destined to lead Asia and establish a Greater East Asia Co-Prosperity Sphere. National pride and the pursuit of self-sufficiency drove Japan’s aggressive actions in Manchuria and later in China, seeking to establish Japan as a preeminent power in the region.

Japan's domestic political landscape in the 1930s was marked by increasing instability and dissatisfaction with the existing government, paving the way for militarism. The global economic depression, coupled with the perceived ineffectiveness of the democratic government in addressing economic and social issues, led to public disenchantment. This environment enabled military leaders, who promised stability and national rejuvenation, to gain significant influence. Political assassinations and military insubordination further weakened the government's authority. The military's promise of restoring national pride and expanding territorial control resonated with the public and political elite, facilitating a shift towards authoritarian, militaristic governance. This transition was characterised by the suppression of political opposition and increased military control over the government, laying the groundwork for Japan’s aggressive foreign policy.