Pearl Harbour

On 7 December 1941, Japanese naval and air forces attacked the American Pacific Fleet base at Pearl Harbor on the Hawaiian island of Oahu. No declaration of war was made. The attack was one of the most important events of the twentieth century. It brought the United States of America into the Second World War and, together with the German assault on the Soviet Union in June 1941 and Hitler's declaration of war on America on 11 December, turned a series of regional campaigns into a true world conflict. Although two mighty alliances now faced each other, the addition of America's vast industrial power to their cause virtually assured the eventual victory of the USA, Britain and the Soviet Union.

Historical Background 1853-1941
The Japanese attack on Pearl Harbor in December 1941 was the culmination of longstanding rivalry between Japan and the United States of America. In the short term, over the previous decade, relations had worsened significantly as Japan set out on a course of aggressive expansion in Manchuria, China and Indo-China. In the long term, from the mid-nineteenth century, the stunning rise of Japan from feudal state to great power had decisively altered the status quo in the Pacific.
Like Germany in Europe, Japan emerged late as a modern nation to challenge the established order. However, so rapid was its modernisation that, by 1900, Japan was the major power in east Asia. Largely lacking the raw materials needed to underpin industrial growth and with an increasing population to sustain, the Japanese were compelled to look overseas for land and resources.
By 1910, Japan had defeated China and Russia in battle and gained control of Korea and Manchuria. Japan's new found strength alarmed the Western powers, particularly the USA. 1907 was the first year in which the US foresaw the possibility of war with Japan. The First World War strengthened Japan's position in east Asia. European influence was weakened or eliminated, allowing Japan to consolidate its gains in China.
In the 1920s, American leadership prevented further Japanese expansion by binding all the leading powers into a new treaty system. However, at home Japanese policymaking was increasingly dominated by a virulent nationalism which saw territorial conquest as Japan's destiny. The onset of the worldwide Depression in 1929, in which Japan suffered severely, triggered a decade of Japanese aggression. The occupation of Manchuria, begun in September 1931, was followed by the annexation of territory in China in 1933 and 1935 before full-scale war between the two countries broke out in July 1937. Japan gradually withdrew from the agreements of the 1920s to sign pacts with the fascist powers Germany and Italy in 1936 and 1940.
War in Europe gave Japan the opportunity to threaten vulnerable British, French and Dutch possessions in the Far East. However, advances into French Indo-China in 1940 and 1941 provoked intense political hostility from the USA which imposed severe sanctions, on oil in particular. Without oil, the Japanese felt their national survival was threatened and they were, therefore, presented with a stark choice. Either they could, at America's behest, give up the gains of the last ten years and have their supplies of vital raw materials restored or they could go to war with the United States. Believing war would achieve their aims (strategic background), the Japanese attacked the USA on 7 December 1941.

The Rise of Japan 1853-1914
The first, distant seeds of the attack on Pearl Harbor were sown in July 1853 by Commodore Matthew Perry of the United States Navy when he sailed uninvited into Tokyo Bay. Less than 90 years before its attack on the US Pacific Fleet, Japan was a country inward-looking and isolated from the outside world, with a largely feudal system of government and way of life. For the past two centuries it had followed a policy of excluding foreigners. In the previous decade, representatives of various Western powers had tried unsuccessfully to establish commercial relations with Japan. The United States, however, anxious to obtain fuel and supplies for its Pacific merchant fleet, was determined to force the Japanese to open up their country.
Unable to resist Perry's show of naval strength, the Japanese signed a treaty with the Americans in 1854, conceding to them diplomatic and trading privileges. Similar agreements with other Western nations soon followed. The shock of this abrupt foreign intervention, together with existing domestic tensions, caused a major political upheaval. As a result, in the late 1860s, Japan emerged from its seclusion to embark upon a period of rapid modernisation as fundamental as its post 1945 economic transformation, looking to the West as the model for its new political institutions, industry and armed forces. Within thirty years, Japan had become the major power in east Asia.
Japan moved quickly to exert its new status. Attempts at revising the unequal trading treaties began as early as 1871 but did not reach fruition until 1894. Growing Japanese influence in Korea, which had the coal and iron resources that Japan lacked, provoked several incidents with China in the 1880s and led to war in 1894-5. With convincing victories on land and sea, Japan defeated the weak Chinese Empire and won significant concessions. China ceded territory, including Formosa (Taiwan) and the Liaotung Peninsula in Manchuria, and gave Japan all the trading privileges on Chinese territory already enjoyed by Western powers. Military success brought international prestige but not yet political power. France, Germany and Russia refused to endorse Japanese gains and insisted upon the return of the Liaotung Peninsula to China.
Nevertheless, this was only a temporary check to Japan's progress. In 1900, it sent the largest contingent to the international relief force which quelled the anti-foreigner Boxer Rebellion in China. In 1902, spectacular recognition was gained when Japan signed an alliance with the world's leading power, Britain. The treaty was designed to check Russian ambitions in the Far East, but also safeguarded respective British and Japanese interests in China and Korea. Then, three years later, Japan decisively defeated Russia, a major Western nation, in the war of 1904-5, caused by growing rivalry in Korea and Manchuria. The victory gave Japan control of Korea (annexed in 1910) and Russia's economic and political interests in Manchuria and forced Russia to abandon its expansionist policy in the region.
Other Western powers were becoming fearful of Japan's new found strength. In 1907, both France and the USA negotiated treaties with the Japanese to safeguard their possessions in this region. The US, in particular, was beginning to regard Japan as a strong competitor in the Pacific and, from this time, both countries could foresee the possibility of war with the other.

The First World War 1914-1918
By the outbreak of the First World War, Japan had an army of over 300,000 men, the fourth-largest navy in the world and a booming economy which could produce many of the armaments it needed. Japan was now the strongest power in east Asia and took full opportunity to strengthen its position while the European states were distracted elsewhere.
As a consequence of its alliance with Britain, Japan fought on the Allied side, declaring war on Germany on 23 August 1914. It moved quickly to seize Tsingtao, the only German port on the Chinese coast, and German island possessions in the Pacific. Apart from sending light naval forces to the Mediterranean in 1917-18, however, Japan was not otherwise involved militarily in the war.
The rise of Japan over the last sixty years had created significant problems. To feed a growing population and acquire the cheap and plentiful raw materials which were not present at home but were essential for sustained success, expansion overseas was vital. In January 1915, Japan moved to exploit the temporary power vacuum in the region by presenting the Chinese with the "Twenty-One Demands". This harsh ultimatum was designed to extract widespread political and economic concessions to make Japan the dominant colonial power in China.
Although the Chinese capitulated on many issues, they managed to resist the most extreme Japanese demands, the acceptance of which would have turned China into a Japanese puppet state. Japan's rapacious policy towards China, driven by an awakening nationalism which fuelled the belief that Japan deserved a special position in that country, left a significant legacy of bitterness and mistrust between the powers after the war.
The First World War changed the political situation in east Asia. It had eliminated German and Russian influence and weakened that of Britain and France in the long term. The USA and Japan, which without an active involvement in the conflict had been spared the cost and had taken the chance to strengthen its trade and industry, were left to struggle for supremacy in a China weakened by civil war between Nationalists and Communists. Despite acquiring the former German Pacific colonies as mandated territories, Japan felt aggrieved that its objectives were not fully realised at the Paris Peace Conference. This sentiment added to the feeling that, just as in 1895 and 1905, the potency of its military victories had been watered down by political interference from the West, which looked down upon the Japanese as racially inferior.

American Leadership 1919-1929
By the end of the First World War, Japan's main rival in the western Pacific region was the United States. America had acquired its own possession in the Philippines in 1898 and annexed Hawaii, Guam and Wake Island, but was behind the other powers in its commercial exploitation of China. Worried by growing Japanese power, the US had embarked upon an ambitious naval building programme before the war and committed to constructing a navy "second-to-none" during it. Japan responded with its own new ships as a direct counter move.
To restrict Japanese expansion by forging a new order for east Asia and the Pacific, but also to respond to the adverse financial climate of the early 1920s, America brought the major powers together in Washington over the winter of 1921-2. The USA, Britain, France and Japan signed a pact to respect each other's Pacific colonies for ten years and agreed to consult if disputes arose. A nine power agreement recognised China's independence, territorial integrity and open door commercial status. A naval arms limitation treaty between the US, Britain, France, Japan and Italy set a ratio of capital ships to be held by USA, Britain and Japan at 5:5:3. They agreed to abandon their existing capital ship programmes for ten years, subject to certain exceptions, and to scrap ships already built or under construction. The Japanese protested unavailingly at this disparity, even though their fleet still maintained its superiority in Asian waters. Yet again, they felt denied equality with the West. Moreover, the stabilising influence of the 1902 Anglo-Japanese alliance was lost when Britain, forced by the US to choose between American and Japanese friendship, did not renew the treaty in 1921.
For the moment, Japan had bowed to the force of American power politics. However, frustration at the lack of progress overseas was fomenting unsettling changes to the established order at home. Public displeasure at the naval treaty compelled the Cabinet to resign. Numbers of extreme nationalist factions, angry at the perceived insults of the West (particularly at the Paris Peace Conference), were growing rapidly. These groups were having an increasing influence on both civilian and military life, often employing violence as a prime tactic. Political assassinations became common; in the thirty years before Pearl Harbor, six Prime Ministers were murdered.
In the 1920s, the army and navy, which held powerful positions of influence within the political hierarchy, became increasingly unruly. The army, in particular, was gripped by the same extreme nationalism which had taken root in other areas of society. Such extremists, which included officers of all ranks among their number, were successful in acquiring a strong grip on the Japanese Army in Korea and Manchuria. The two services had divergent foreign policy aims. The army advocated expansion on the Asian mainland, where the Soviet Union would be the enemy. The navy looked outward across the Pacific, where it would encounter the Americans, as it searched for supplies of oil vital for Japanese survival.

Japanese Aggression 1929-1939
The desire for expansion, which many Japanese felt was vital to ensure national survival, was increased by the onset of the worldwide Depression in 1929. Japan suffered severely from the slump, with its rural economy particularly badly hit. As a direct response to the distress at home, the first move was made by the Japanese army of occupation in southern Manchuria, the strongly pro-nationalist Kwantung Army. In September 1931, an alleged act of aggression by Chinese troops at Mukden (actually fabricated by the Japanese) was used as a pretext for the Kwantung Army to occupy the whole of Manchuria.
The invasion, which was widely popular in Japan, had two important consequences. It demonstrated the weakness of the civilian government, which had been powerless to stop the campaign, and began a period where the armed forces were the predominant influence in Japanese politics. It also had a profound effect on Japan's international situation. Despite further Japanese aggression, against Shanghai in January 1932, Britain and America did little. Strategically, military action was not feasible as Japan was too far away. Economically, neither country wanted to damage the valuable trade they had built up by the 1930s. However, to the West, it was now clear that Japan, which had defied the League of Nations by moving against Manchuria, was a danger to the status quo.
Japan left the League in 1933 after being censured for its actions in Manchuria. In 1933 and 1935, Japan annexed further territory to gain control of China north of the Great Wall. In 1934, in violation of the international "open door" agreement, Japan warned other powers that it considered China as within its commercial sphere of influence. In January 1936, having failed to win equality with Britain and America, Japan withdrew from the naval limitation agreements first signed in Washington in 1921. In November 1936, in an attempt to check Soviet expansionism in the Far East, Japan signed the Anti-Comintern Pact with Germany.
On 7 July 1937, after a minor incident at the Marco Polo Bridge near Peking, war broke out between Japan and China. Any remaining vestiges of Western tolerance evaporated; Japan had now renounced all the elements of the collective security system established at Washington in 1921. Peking and Tientsin fell quickly but, with the stiffening of Chinese resistance, the Japanese soon realised it would not be the short campaign they envisaged. In August, bitter fighting broke out in Shanghai. In December, the Japanese captured Nanking, the Nationalist capital, amid scenes of savage brutality. The Japanese Army, which by now had over 700,000 troops in China, won impressive victories in 1938. But the vastness of the country and the increasing use of guerilla tactics by the Chinese inexorably sucked the Japanese into a war of attrition, which would endure until 1945.
By 1939, the war was costing $5m per day, adversely affecting Japan's industrial expansion and restricting its ability to pay for the vital finished goods and raw materials it needed from the rest of the world. Clashes with Soviet forces in Mongolia brought heavy defeats. In August the Anti-Comintern Pact fell into abeyance as Nazi Germany signed a Non-Aggression Pact with the Soviet Union. By September 1939, little credibility remained in Japan's policy of expansion. Then on the other side of the world one event transformed the situation: war broke out in Europe.

Countdown To Attack 1939-1941
The outbreak of war in Europe in September 1939 was timely for Japan. Deeply committed to a long war of attrition in China, assailed by the Soviet Union in Manchuria and outstripped by American naval rearmament, the success of Japanese expansionism was under threat. However, for the second time in twenty years, the struggle between Britain, France and Germany in a European conflict presented Japan with opportunity. Germany's defeat of France and the Netherlands by mid-1940 left the latter's Far East colonies without protection. Britain, preparing to repulse the Luftwaffe, was also in no position to counter an Asian predator. Politically too, Japan recovered. In June 1940, accommodation was reached with the Soviets in Manchuria and, in September, a tripartite alliance was signed with the like-minded Germany and Italy. By promising mutual assistance to any signatory attacked by a country not already at war in Europe, it gave Japan a perception of security when dealing with the United States.
However, confrontation with the United States came quickly. In July 1940, America warned Japan not to advance into Indo-China, though the Japanese had already coerced France and Britain into closing supply routes from there and Burma to China. Much more significantly, the US imposed restrictions upon exports of oil and steel to Japan; America supplied 80% of Japan's oil. The deterrent did not work. As the embargo already directly threatened Japan's survival, the Japanese went ahead with landings in Indo-China in September. Positions in the north were consolidated over the winter in preparation for a new offensive in July 1941 to swallow up the rest of the country.
The conquest of the southern territories would bring the raw materials so vital to Japan. No better opportunity to carry it out would arise as the German invasion of the Soviet Union on 22 June had removed the immediate Soviet threat in Manchuria. Unfortunately for the Japanese, the occupation of the rest of Indo-China hardened the US position. On 25 July, America froze all Japanese assets in the USA and imposed a total oil ban. Britain and the Netherlands followed suit. A decisive moment in Japanese history had arrived. As Japan's oil supplies were now decreasing too rapidly to sustain its territorial expansion, a stark choice presented itself. Either Japan could attempt to restore essential supplies by improving diplomatic relations, which seemed unlikely, or continue its conquests southward and go to war with the United States.
The precarious oil supply position did not give Japanese diplomats much time. After a period of political infighting, on 6 September the leadership decided that preparations must be made to go to war by early November. Genuine attempts were made by the Japanese to negotiate a settlement, but US demands for a total withdrawal from China and Indo-China were completely unacceptable. After a delay due to a change of Cabinet, on 30 November the Japanese Emperor, Hirohito, gave his assent to the plans for war. The Americans, who had broken the Japanese diplomatic code, were fully aware of these events, but they did not know where Japan would strike. Six days later, Japanese naval and land forces began assaults on Malaya, Hong Kong and the US Pacific Fleet at Pearl Harbor.

Strategic Background: Why Pearl Harbour?
By the beginning of the twentieth century, Japan's emergence as the leading power in the western Pacific made it a natural political and economic competitor of the United States of America. Rivalry between the two countries over commercial and territorial interests in the region grew from this time. As early as 1907, both nations could foresee the possibility of war with the other.
Any conflict, at least initially, would be a naval war. Japan realised that its navy was not, and never would be, the equal of the United States Navy. The Japanese expected the American fleet to move west and attack. To counter any such move, in the 1920s and 1930s, the Japanese planned a defensive strategy of attrition. Starting west of Hawaii, submarines, carrier-borne and land-based aircraft and light naval forces would attempt to destroy as many US ships as possible (up to 30% of the fleet it was hoped) as it sailed west before Japanese battleships moved in to win a decisive victory in home waters. When the Second World War broke out, the Japanese Navy enjoyed local superiority in the Pacific as America had not constructed the maximum number of ships allowed it by current international agreements. However, in the face of continuing Japanese aggression in Asia and crushing German victories in Europe, in July 1940 the USA decided upon a massive naval expansion. Within a few years, Japan's advantage would have disappeared.
By 1940, the Japanese Army's campaign in China was making no progress. The navy offered an alternative strategy of a southward advance into Indo-China and the oil-rich Dutch East Indies. The execution of this policy from September 1940 onwards severely antagonised the USA and brought great risk of war. When, in July 1941, the US imposed a total oil embargo on Japan, the Japanese saw conflict as inevitable and began planning accordingly.
It was in this context that Admiral Isoroku Yamamoto, Commander-in-Chief of the Combined Fleet, suggested an air attack on the US Pacific Fleet, which had moved from its usual base at San Diego on the American west coast to a mid-Pacific location at Pearl Harbor in May 1940.
Yamamoto's plan was a development of the traditional Japanese defensive strategy. He gambled on a surprise attack to destroy the American naval capability in the Pacific, including its all-important aircraft carriers, and create enough time, perhaps six months, to enable Japan to complete its territorial conquests. Simultaneous attacks by the army on Hong Kong, Malaya, the Philippines, Guam and the Dutch East Indies would capture the strategically important bases and areas rich in raw materials Japan felt was vital for its national survival and would also now be needed to sustain its war with America. A long struggle was expected, but it was hoped that the inevitable American onslaught would founder on the fortified defensive ring the Japanese would create around their empire.