Japan's response to world developments in the 1930s

Despite the US policy of isolationism, the USA responded to Japan's invasion of China in 1937 by placing restrictions on Japanese trade with the USA. The USA went further and imposed a trade embargo on Japan, banning the sale of fuel, iron and steel to Japan when Japan invaded Vietnam in 1940, These resources were essential to support Japan's war effort in China.

The trade embargo not only soured relations between Japan and the USA but also
undermined Japan's war effort and jeopardized its chances of success in China unless it found new alternative sources. Refusing to abort its war in China, Japan was left with the only option of seeking alternative sources and this made control of resource-rich countries in Southeast Asia very attractive.

Thus Japan responded to the USA's imposition of trade embargo by attacking the US base in Pearl Harbor and invading Southeast Asia. These responses brought it into direct confrontation with the USA, causing the outbreak of war in 1941.

Japan decided to invade Southeast Asia because it needed to find resources to sustain its war effort in China. However, the US Pacific Fleet based at Pearl Harbor posed a formidable deterrent and threat to a Japanese invasion of Southeast Asia, as it had the necessary air and sea power to check Japanese advance and defend Southeast Asia. Thus Japan decided to remove this possible threat by attacking the US fleet at Pearl Harbor. Japanese navy and army chiefs told the Japanese Prime Minister and Emperor that war with USA was inevitable and also advised them that a quick 'knockout' blow against the
USA and rapid southward advance would force the USA to negotiate a peace settlement. In October 1941, Prime Minister Konoe, who preferred negotiation to war, resigned and the War Minister, Hideki Tojo, was appointed as the new Prime Minister.

With Tojo, a militarist, in power, it cleared the stage and set the aggressive mood for Japan's
attack on Pearl Harbor. The Japanese Emperor approved Tojo's plans for war against the USA and this started the war in Asia-Pacific.

Thus the Japanese attack on Pearl Harbor triggered the start of the war in the Asia-Pacific,as its aggressive action made the USA retaliate and declare war on Japan on 8 December

The outbreak of war in Europe in 1939 and the fall of the European powers like France to
Germany critically weakened and depleted their defences of their colonies in Southeast Asia.

The European powers' preoccupation with the war in Europe meant that Southeast Asia
was left vulnerable and poorly defended, making it an easy target for Japanese aggression.

Thus the war in Europe contributed to Japan's decision to wage war in the East, as it created
an opportunity for the Japanese to take advantage and seize control over Southeast Asia, leading to the outbreak of war in the Asia-Pacific.