WW2 · CHAPTER 7 ·
Japanese expansion and Pearl Harbor
Chapter 7 of The War Room — WW2, 1936–1945: “Rising Sun: From China to Pearl Harbor”
Japan invaded China in 1937 but could not force a surrender, and its occupation brought mass atrocities such as the Nanjing Massacre. When it occupied southern Indochina in 1941, the US cut off its oil. Japan struck Pearl Harbor on 7 December 1941 and swept through Malaya, Singapore, the Philippines and the Dutch East Indies.
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The map above is the world of Asia and the Pacific, May 1942 — The hundred days.
Every state on the map that year: The world in 1942 · Europe in 1942.
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SHORT EXPLANATION
Japan’s war with China helps explain why its leaders attacked Pearl Harbor. After invading in 1937, Japan seized cities, ports and railways, but the Chinese government fought on. At Nanjing, Japanese forces murdered and raped civilians and prisoners on a vast scale. The victims’ suffering is part of the history of occupation; China’s resistance also kept much of the Japanese army committed for years.
In 1941 Japan occupied southern French Indochina to increase pressure on China. The United States responded with an oil embargo, threatening Japan’s capacity to fight. Japanese leaders chose to take Southeast Asia’s resources and strike the American Pacific Fleet rather than withdraw. The attack on 7 December brought America into the war, but the carriers were at sea and Pearl Harbor’s fuel tanks and repair yards remained largely intact.
The full story
Japan’s war in China had already lasted four years when its leaders decided to attack the United States. Japan had seized Manchuria in 1931 and launched a full-scale invasion of China in 1937. Its armies took coastal cities and railways, but these victories did not bring surrender: the Chinese government withdrew inland to Chongqing and continued the war.
Occupation inflicted systematic violence on the population. At Nanjing, Japanese forces murdered and raped civilians and prisoners on a vast scale. These crimes belong to the history of human suffering, not to a calculation of moves in a contest. China’s continued resistance had a strategic consequence as well: it kept a large share of the Japanese army in China for years.
The occupation of southern French Indochina in 1941 was intended both to tighten pressure on China and to prepare a move south. The United States froze Japanese assets and cut off oil. Japan imported roughly 80 percent of its oil, mostly from the United States, so its reserves placed a limit on how long it could sustain operations. Japanese leaders rejected withdrawal and decided to seize the oil of the Dutch East Indies. First, they would try to cripple the American power that might interfere.
Six carriers attacked Pearl Harbor on 7 December 1941. They sank or damaged battleships, but the American carriers were at sea, and the fuel and repair facilities remained usable. Japanese forces then swept through Malaya, Singapore, the Philippines and the Dutch East Indies. In a hundred days Japan gained an immense empire. Holding it was another matter: each garrison depended on long sea routes that Japan’s merchant fleet and escorts could not reliably protect.
The decision for war reflected an institutional deadlock as well as a shortage of oil. The army refused to abandon China; the navy warned that dwindling fuel would eventually make a southern campaign impossible. A blow at Pearl Harbor and a fortified perimeter, Japanese leaders hoped, would buy time and persuade the United States to negotiate. For that plan to work, America had to accept its losses instead of mobilizing its much larger economy. The attack united American opinion for war, and Germany’s subsequent declaration of war on the United States joined the Asian and European wars. Japan had won its perimeter, but it faced an enemy able to grow stronger while its own empire was overextended.
FULL EXPLANATION
Escalation from the China war
The China war consumed men, money and fuel without producing the surrender Japan sought. Withdrawal threatened the army’s prestige and made the sacrifices already endured seem wasted. A southern advance offered oil and raw materials, but it would also bring war with the United States, Britain and the Netherlands. The costs already incurred made a further commitment attractive, even though taking resources in the south would not itself end the war in China. That is the sunk-cost pattern at work. Rival army and navy priorities, weak civilian cabinets and the difficulty of reversing imperial policy made a change of course harder. The American embargo helped determine the timing, but it did not make Pearl Harbor inevitable: Japan’s leaders chose to preserve their empire at the risk of war with a far stronger enemy.
Tactical success, strategic failure
At Pearl Harbor Japan achieved surprise and temporarily disabled much of the American battle line. The intended result was larger: with the United States shocked and a defensive perimeter established, Japanese leaders hoped America would negotiate. The attack instead united American opinion against compromise. Nor had the strike removed all the means for a return. The carriers were absent, the submarines survived, and Hawaii’s fuel tanks and repair yards remained usable, allowing damaged ships to be raised and rebuilt there. Japan bought time for its southern conquests, but could not stop American mobilization. Its opponent’s industrial capacity was vastly greater. The immediate military success thus left Japan farther from the political settlement it needed.
Key places on the map
On this day
Why it happened
An empire built on imported oil. Japan depended on imports for 80% of its oil, mostly from the United States. After the move into Indochina, the July 1941 embargo cut that supply. Existing reserves would support operations for a time, but a southern campaign would become harder as they ran down. The shortage helped set the timetable for Pearl Harbor.
The China quagmire. Chiang Kai-shek’s government yielded space and kept fighting. Four years of Japanese victories had brought territory, but no Chinese surrender. The army pressed for wider war; abandoning the campaign would mean relinquishing gains after heavy sacrifices, while further escalation seemed to offer a way forward.
Khalkhin Gol turns Japan south. At Khalkhin Gol on the Mongolian border in summer 1939, Soviet forces under Zhukov defeated a Japanese army. Tokyo later signed a neutrality pact with Moscow and turned toward the resource-rich European colonies to the south. The pact also helped the Soviet Union transfer forces from the east when Moscow was threatened.
The knockout-blow theory. Admiral Yamamoto had studied at Harvard and opposed the war. If Japan had to fight, he argued, it should strike the US fleet on the first day and establish a buffer costly enough to persuade America to negotiate. He doubted Japan’s prospects beyond the opening period: “I shall run wild for six months … after that I have no expectation of success.”
THE TURNING POINT
Pearl Harbor, 7 December 1941. Japan achieved surprise, hitting eight battleships for the loss of 29 aircraft. Yet the carriers were at sea, and the oil tanks and shipyards were barely touched. The blow damaged the fleet Japan feared while helping unite a divided, isolationist American public for war.
What it changed
The sleeping giant. American industry was only one-tenth mobilized when war began, but within a year it out-produced the Axis. By 1944 the United States launched more ship tonnage in a month than Japan built in a year. Yamamoto’s warning about the first six months proved almost exactly right: Japan’s early advantage gave way to American production.
Hitler’s strangest decision. Germany declared war on the United States four days after Pearl Harbor, although it was under no obligation to do so. America now faced Germany as well as Japan, and Roosevelt’s “Germany first” strategy no longer faced the same political obstacle.
Empires lose their aura. Singapore’s surrender put 80,000 troops into the hands of a smaller Japanese force. The defeat shattered the image of European invincibility in Asia. The upheaval of 1942 became part of the history leading to independence in India, Indonesia and Vietnam.
DISCUSSION QUESTION — How could Pearl Harbor be a successful surprise attack and a strategic mistake?
The attack damaged the American battle line and gave Japan time to conquer territory. But the carriers and key base facilities survived, and American opinion united for war. Japan needed a negotiated settlement before superior US industry took effect; instead it faced full mobilization.
An interesting fact
Tokyo intended a note breaking off negotiations to reach the United States about half an hour before the strike. It arrived in fourteen parts, and embassy diplomats, ordered to show it to no secretary, typed it themselves and badly. They delivered it nearly an hour after the bombs fell. American codebreakers reading the “Magic” intercepts had decoded it before the embassy finished. Even on time, the note would have ended talks rather than declared war.
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