Final answer:
The Japanese justified the attack on Pearl Harbor as essential to prevent U.S. interference with Japan's empire expansion in Asia and to exploit the vulnerable state of European colonies. U.S. embargoes and diplomatic tensions also contributed to Japan's decision. The attack was aimed at crippling American naval power, but it propelled the U.S. into full wartime mobilization.
Step-by-step explanation:
Justification of the Attack on Pearl Harbor
The Japanese military planners justified the attack on Pearl Harbor as a strategic necessity to secure Japan's empire expansion in Asia. Citing the vulnerability of Southeast Asian colonies due to European conflicts, Japan sought to acquire raw materials such as rubber, oil, and tin to support their Greater East Asia Co-Prosperity Sphere. Believing that the United States' interference in their expansion was inevitable, they aimed to cripple the U.S. naval presence in the Pacific to prevent opposition to their conquests. The coordinated attacks across the Pacific were meant to neutralize U.S. and European powers, providing Japan time to fortify positions and continue territorial expansion.
In the face of U.S. trade embargoes and demands for Japan to withdraw from China and Southeast Asia, Japanese officials felt there was little reason to maintain diplomatic relations. The surprise attack on Pearl Harbor was deemed necessary to ensure no interference would come from the U.S. while Japan took advantage of the weakened state of European colonies in Asia. The attack aimed to destroy significant portions of the U.S. Pacific Fleet to hinder American military response capabilities. However, this attack ultimately led the American public and its leaders to rally against Japan, transitioning from a peacetime economy to a wartime mobilization famously known as the Arsenal of Democracy.