Without warning or even declaring war, Japan attacked the US naval fleet at Pearl Harbor, Hawaii, on 7 December 1941. Japan's military government, which had already occupied Manchuria, Korea, coastal China, and French Indo-China, needed access to raw materials, particularly oil, to continue its imperialist ambitions in the Pacific. A pre-emptive strike on the US Navy, it was hoped, would allow Japan to dominate this theatre of the Second World War (1939-45).
Although the attack destroyed battleships and caused over 3,500 casualties, the US aircraft carriers were not in Hawaii at the time, and vital supply dumps were left intact. As a consequence, after the US entered the war in response to the raid, the US Navy was able to eventually recover. Ultimately, the US armed forces defeated Japan with devastating consequences for its population in August 1945.
The reasons Japan attacked Pearl Harbor include:
- A long run of victories and territorial acquisitions in South East Asia going back to the 1870s gave the Japanese navy confidence it could defeat anyone.
- Defeats to Nazi Germany by the Netherlands, France, and Britain in Europe in 1940 meant they were less likely to be able to defend their territories in the Pacific.
- A peace treaty with Russia signed in April 1941 meant Japan was free to concentrate on expansion in the Pacific.
- Japan's land war with China had dragged on longer than expected, and so the Japanese navy argued that expansion could better be achieved in other areas of the Pacific.
- The US embargo on the sale of oil and other raw materials to Japan in 1941 meant the state was obliged to seek resources through conquest.
- A preemptive surprise attack on the US fleet would weaken it to the extent that Japan would have a free hand in the Pacific for the foreseeable future.
- If Japan could swiftly occupy all of resource-rich South-East Asia, then the US, without a significant navy, might maintain its isolationist policy and sue for peace.
Japanese Expansion in the Pacific
The British and Dutch empires had long possessed valuable territories in the Pacific region, notably Malaya and the Dutch East Indies (Indonesia). Hawaii, the Philippines, and Guam were all acquired by the United States in 1898. Japan was equally keen to forge its own empire and expand its influence in the Pacific, starting with the occupation of the Ryukyu, Bonin, and Kurile Islands in the 1870s. In 1894-5, China and Japan were at war (First Sino-Japanese War), and the latter acquired Formosa (Taiwan) and the Pescadores Islands. Another victory for Japan followed against Russia in 1904 (Russo-Japanese War). Korea was fully annexed by 1910. During the First World War (1914-18), Japan was an ally of Britain, France, and the United States, and when victory was achieved, its reward was to receive control of some of the losing Germany's colonies in the Pacific. The Japanese possession of the Mariana, Caroline, and Marshall Islands meant that the United States would be hard-pushed to defend its interests in places like the Philippines.
Japan's Military Government
In the 1930s, a Japanese military government was established, swept into power following a series of social and economic problems, disruption caused by a series of earthquakes, and with the promise that it would defend Japan against perceived foreign threats. The emperor, Hirohito (reign 1926-1989), had limited powers as a constitutional monarch and was really there only to formally legitimize decisions taken by the military government. Japan's population had been rising by one million each year, and the country's resources were stretched to breaking point. The situation was exacerbated by the Great Depression of 1929 and a slump in world trade. In 1932, the recovering economy, boosted by the devaluation of the yen following the collapse of the international gold standard, was helped by massive government spending on armaments. The expansion of the military, however, required equally massive quantities of raw materials Japan simply did not have.
Japan had openly challenged the League of Nations and international peace when it occupied Manchuria in September 1931. This region of north-east China was rich in natural resources and had a geographical position of strategic importance. The Chinese government had neglected the region somewhat and its lawlessness jeopardised Japanese trade interests there. A Japanese puppet state, Manchukuo, was established in March 1932. The League of Nations failed to deliver an effective response. Most member states were unwilling to impose economic sanctions that would limit trade during a world economic crisis. Japan renounced its membership of the League in March 1933. This was perhaps just as well since the country fell even lower in the esteem of League members when it started an all-out war of conquest in China in July 1937, the excuse being Japan wanted to protect its assets in China against the increasingly powerful Chinese nationalists. Japan's government was increasingly made up of hardline imperialists, and in 1937, it took full control of the country's industries, labour, and press. The economy, particularly heavy industry and shipbuilding, was increasingly put on a war footing. By 1937, the Japanese government was already spending 65-75% of its total budget on the military, more than double the figure spent in 1931.
Japan then allied itself with the two other aggressive states in world affairs, Fascist Italy and Nazi Germany, signing with them the Anti-Comintern Pact, a treaty of mutual cooperation in empire-building and a united front against communism. A setback to Japanese expansion came in the summer of 1939 when its forces were defeated by those of the USSR in the border region between Manchuria and Outer Mongolia. The Japanese army suffered 18,000 casualties at the battle of Nomunhan (aka Khalkhin Gol). This defeat gave the Japanese navy one more argument in its favour that the Pacific should be Japan's next area of expansion.
Despite the loss to the USSR, Japan's long run of victories over the last 65 years gave the Japanese military government an overconfidence that its armed forces were superior, certainly to those of the European nations defeated by Nazi Germany and even perhaps to the, as yet, untested United States' armed forces. Many Japanese had been educated from a young age to believe they were superior to everybody else because of their race, culture, and unswerving determination to serve their emperor. In short, the military government could persuade the population that Japanese domination of the Pacific was inevitable.
The Resources of South East Asia
Japan turned to Southeast Asia in its search for imperial glory and natural resources, especially oil, the import of which was restricted by a US embargo. This embargo was imposed to induce Japan to withdraw from China and protect US interests in places like the Philippines. Japan's war economy desperately needed imported oil (Japan could only produce 6% of its requirements), iron ore, coal, lead, tin, rubber, and nickel. Significantly, at least two-thirds of imported oil came from the US in 1936. The Japanese government had begun to stockpile raw materials, but this policy, although prudent, would not be enough to meet the military's needs if war broke out with the US and its allies.
The Japanese military hoped that events in Europe, where WWII had begun with Germany's invasion of Poland in 1939, would prevent any direct reaction against their aggressive expansion in the Pacific. That year, Japan occupied Hainan Island and the Spratly Islands. Military defeats suffered by the Netherlands, France, and Britain in Europe in 1940 led some Japanese militarists to believe these states would now be much less able to defend their territorial assets in the Pacific. This was particularly so for the Netherlands and France, which were wholly or partially occupied by Nazi Germany by June 1940. Nevertheless, the Netherlands still controlled the Dutch East Indies and France still had the group of colonies collectively known as Indo-China (which included what is today Laos, Cambodia, and parts of Thailand).
In September 1940, Japanese forces occupied the northern part of Indo-China. In the spring of 1941, Japan occupied several key southern ports in China. In April 1941, a Soviet-Japanese non-aggression pact was signed, which permitted Japan to concentrate on its growing empire to the south. In July 1941, Japan attacked southern Indo-China. The only major obstacle to further Japanese expansion in the Pacific was the United States.
US Isolationism
Through the late 1930s, the United States, fully aware of Japan's imperial ambitions in the Pacific, had attempted to impede Japan's ability to wage war. By June 1941, US economic sanctions were blocking the export of crude oil, gasoline, copper, iron, and steel to Japan, as well as many other raw materials necessary for military development. British Malaya and the Dutch East Indies also blocked oil exports to Japan. A general trade embargo effectively reduced the US trade with Japan by three-quarters. The US and Britain were actively supporting Chiang Kai-shek, the Chinese nationalist leader, in his efforts to prevent further Japanese expansion. Meanwhile, Japanese financial assets in US banks were frozen, severely limiting Japan's ability to buy oil. The US, as it was doing in the European theatre of WWII, was essentially doing all it could to impede an aggressor state short of military action.
Japan responded to the oil embargo by declaring its intention to create a new economic zone, the Greater East Asian Co-prosperity Sphere. Such countries as Australia, the Philippines, India, Burma, and Malaya would be obliged to join this sphere since the Japanese government declared they would treat any state not willing to join it as an enemy. The trade embargo, then, seemed to be having the opposite effect intended. Japan was not going to limit its imperial expansion but ramp it up several gears.
On 1 December 1941, the Japanese government decided it would declare war on the United States, Britain, and the Netherlands. The Japanese government felt that, sooner or later, these states would declare war on Japan anyway if it continued its expansion in the Pacific, particularly if it attacked the oil-rich areas of British Malaya and the Dutch East Indies. An attack on the US' allies Britain and the Netherlands would surely provoke this sleeping giant into finally entering the war. Consequently, a secret aerial attack on the US naval base at Pearl Harbor, Hawaii, would, it was hoped, remove the United States from the Pacific War before it even got started. The destruction of as many US ships as possible would be essential since the Japanese navy could not compete with the numerically larger US Navy and much more powerful economy of the US in the long term. A short, sharp victory, however, might allow Japan to keep its ill-gotten territorial gains. The US might even choose, with no significant naval force in the Pacific, to continue its policy of isolationism and seek a peace deal with Japan.
The Attack
The plan of attack was made a reality by Admiral Yamamoto Isoroku (1884-1943), Commander-in-Chief of the Combined Fleet. In the planning stage, it was realised that, in order for the attack to be a success, it must have absolute surprise, involve at least six of Japan's largest aircraft carriers so that their aircraft could reach such an isolated target, and involve a large fleet of submarines and support vessels, including refuelling ships. Yamamoto only just convinced Admiral Nagano, Chief of the Naval General Staff, that the ambitious plan could work and an attack on Hawaii was preferable to one on the Philippines, which had long taken priority with Japanese military planners.
A Japanese naval task force would strike out deep into the Pacific in an offensive action that would deal not only a massive material blow to the enemy but also a sharp psychological one. It was an audacious gamble, but one with potentially huge rewards. As Commander Minoru Genda (1904-1989), the man charged with conducting a feasibility study for the attack plan, noted, "It was felt that in the case of war, if Japan were to fight in a conventional way there was little hope of winning" (Holmes, 199).
Yamamoto did have some technological cards in his favour in this game of chance. The Japanese had developed torpedoes that could operate in shallow waters and so be dropped by plane at Pearl Harbor. The US military was unaware of these developments, which led to a complacent belief that their shallow-water base could not be attacked by torpedo-carrying aircraft.
The attack on Pearl Harbor was carried out on 7 December. The Japanese did achieve surprise. US military intelligence was aware that some sort of Japanese operation was underway, but it was felt that the Philippines, just 200 miles (320 km) from Japan's bases on Formosa, would be the most likely place of any attack. Most US commanders were also convinced that any attack on Pearl Harbor, which was some 3,400 miles (5,500 km) from Japan, would take the form of sabotage and submarine attack; they did not imagine a full-scale carrier group would be launched against Hawaii.
It has been suggested that the US military and President Franklin D. Roosevelt (1882-1945) were aware of the planned attack on Pearl Harbor, but the decision was taken not to warn the local commander because such a raid would provide the ideal excuse for the US to actively enter WWII. There is no conclusive evidence supporting this view. If anything, the lack of communication between the intelligence gatherers in Washington, who had intercepted coded Japanese consular messages which highlighted a strong interest in Pearl Harbor, and the commanders in the field was due to interservice rivalries and general incompetence rather than anything else. There were blunders such as sending the latest decoding machine to Britain rather than the base in Hawaii, for example. Similarly, some have seen the US oil embargo as a deliberate attempt to force Japan into an aggressive act that would swing US public opinion into supporting entry into the war, but there is little evidence for this either. It is perhaps a measure of the audacious gamble Japan took that such conspiracy theories seek to explain how the US Navy could have been caught so unaware.
Consequences
The Pearl Harbor attack was an overwhelming success for the Japanese. 94 US ships were based at the harbor. The Japanese task force ultimately sank or seriously damaged 18 ships (including eight battleships), destroyed or damaged nearly 200 US aircraft, and killed 2,403 people and wounded 1,178 (Dear, 680). The Japanese force lost just 29 aircraft and six submarines, most of which were easily replaceable mini-subs. This was a crushing blow, but crucially for future operations, the three US aircraft carriers were on manoeuvres and absent from Hawaii that day. In addition, the bases' fuel depots had not been damaged and so Pearl Harbor could continue to operate. The attack had been a tactical victory but not a strategic one.
The Pearl Harbor attack was not the end but only the beginning of the Pacific War (called by the Japanese the Great East Asia War). Day two of this war also went well for Japan when a raid destroyed the majority of the 35 B-17 Flying Fortress aircraft belonging to the USAAF on Luzon Island in the Philippines. Japan would win many more victories through 1942, but this was a war that it could not win in the longer term given the combined resources of the Allies. Eventually pushed back to defend only its own islands, Japan's war ended with devastating consequences for the Japanese people when two atomic bombs were dropped on Hiroshima and Nagasaki in August 1945.
