Zhai Xiang@ZhaiXiang5
On the morning of December 7, 1941, at 7:48 am Hawaii time, or 1:18 pm Eastern Standard Time, Japan launched a surprise attack on Pearl Harbor. More than 2,000 Americans lost their lives, over 20 naval vessels and nearly 200 aircraft were destroyed. The following day, FDR delivered his famous "Day of Infamy" speech, and the United States declared war on Japan.
For a long time, a conspiracy theory has circulated globally: that the US government had prior knowledge of Japan's plan to attack Pearl Harbor but deliberately allowed it to happen, in order to arouse public anger and build political support for entering the war. When I was in middle school in China, I read similar claims in magazines and newspapers.
There is also a version popular in China that Chinese intelligence agents had broken Japanese military codes beforehand, and Chiang Kai-shek relayed this information to Roosevelt, but it was not taken seriously by the Americans.
While studying at Stanford, I worked part-time at Hoover between 2012 and 2015, during which I was the only research assistant on China. I read every page of Chiang Kai-shek's diaries after 1949 and most of those before 1949. Supported by Stanford's FSI and other institutions, I also conducted archival research at the FDR Presidential Library, as well as Taiwan's Academia Sinica and the Academia Historica. My own research into Chiang's documents shows no evidence that Chinese intelligence had decrypted Japanese communications prior to Pearl Harbor. However, on December 7 at noon, Roosevelt did meet with Chinese Ambassador Hu Shih (胡适) and told him that war between the US and Japan might soon break out. An hour later, back at the embassy, Hu received a personal phone call from Roosevelt, making him the first Chinese to learn of the Pearl Harbor attack.
So, did the United States have foreknowledge of the attack? And why did Japan choose what today might seem like such a reckless way to provoke war with the US? As we approach the 80th anniversary of V-Day marking the end of World War II, I would like to share my findings and reflections, drawn from my archival research.
In 1931, Japan invaded Northeast China and soon established the puppet state of Manchukuo. At the time, the United States, mired in the Great Depression, had little capacity to restrain Japan. Nevertheless, in 1933, the US government issued a statement declaring it would not recognize Manchukuo.
During the 1930s, US–Japan trade relations were close, driven by substantial economic interests. Japan accounted for nearly 10% of America‘’s total foreign trade, more than twice the share of China. Coupled with the widespread isolationist sentiment among the American public, there was little incentive for the US to confront Japan directly.
However, as Japan aggression expanded, American interests were increasingly undermined. At the end of 1937, Japanese aircraft attacked the USS Panay while it was sailing on the Yangtze River. Although Japan later claimed they didn't see the US flag and offered compensation, the incident cast a long shadow over US–Japan relations.
In 1940, Japan occupied French Indochina (approximately today's Vietnam, Laos, and Cambodia) and formally joined the Axis alliance with Germany and Italy. Britain and the United States had once hoped Japan would pursue a "northward" strategy against the Soviet Union, but instead Japan turned to a "southward" advance, inflicting serious damage on their interests. In the summer of 1941, Roosevelt announced an oil embargo on Japan. This was a heavy blow, as it meant Japan's military expansion in Asia could no longer be sustained.
At the top left is the telegram Roosevelt sent to Emperor Hirohito on December 6, 1941 expressing his hope for reconciliation between the United States and Japan. Secretary of State Cordell Hull also cabled US Ambassador to Japan Joseph Grew, instructing him to deliver the full text of Roosevelt's telegram to the Emperor as soon as possible. Unfortunately, although the telegram reached the Tokyo telegraph office at noon on December 7, it was delayed and only delivered to the US Embassy at 10:30 that night. Grew later recalled that when the Embassy contacted the Japanese Foreign Minister, his secretary asked whether the matter was so urgent that it could not wait until the next day. Grew therefore believed that at least the minister's secretary was unaware that war was about to break out. Shortly after midnight on December 8, Grew met the Foreign Minister and requested an imperial audience to deliver Roosevelt's message. The next morning, after 7 am, he was informed that the Foreign Minister had already met Emperor Hirohito at 3 am, the very hour when Pearl Harbor was under attack. The minister handed Grew a memorandum of more than ten pages; the final page stated that Japan believed it was no longer possible to reach an agreement with the US, and that this counted as the Emperor's reply. Clearly, Roosevelt's last attempt to avert war through diplomacy did not succeed.
At the top right is a record from Chiang Kai-shek's archives concerning Ambassador Hu Shih's meeting with Roosevelt on December 7. According to both the White House presidential schedule and Hu's later recollections, on December 6 Hu was in New York attending an event when he was informed he needed to meet Roosevelt. He rushed back to Washington that night and met FDR at 12:30 pm on December 7 for forty minutes. Roosevelt briefed him on the content of the telegram sent to the Emperor, describing it as a final effort for peace, but admitted that the US was not optimistic, predicting that war with Japan would break out within 48 hours. He remarked that such a war would be a tragedy for humanity, but could be a major opportunity for China, and hoped that China would feel sorrow rather than celebration if US–Japan hostilities began. Shortly after Hu returned to the embassy, he received a personal phone call from Roosevelt, informing him that Japanese forces had already begun their attacks on Pearl Harbor and Manila.
According to FDR archival records, at 1:47 pm, in the White House's Yellow Oval Room, FDR was working on his stamp collection when the Secretary of the Navy telephoned to report that Japanese aircraft were bombing Pearl Harbor. At first, Roosevelt's confidant Harry Hopkins thought it must have been a mistake. Minutes later, General George Marshall called with the same report.
At 3:05 pm, FDR met in the Yellow Oval Room with the Secretaries of the Navy and War; Marshall and Hull joined them fifteen minutes later. At 4:15 pm, Roosevelt began dictating to his secretary the draft of his war message to Congress.
In the bottom left corner is the printed draft from his secretary, on which one can see Roosevelt's careful edits. For example, he changed "a date which will live in world history" to "a date which will live in infamy." He also inserted "at the solicitation of Japan" before the phrase "conversation with its government and its emperor." Unlike the usual practice, where the president provided general guidance and speechwriters produced the text, this time Roosevelt wrote the speech himself, and it became one of the most iconic addresses in American history.
The archives also reveal a curious episode about this speech. Hull had requested that Roosevelt present in detail the history of US–Japan tensions and the failure of negotiations. To this end, the State Department prepared a 17-page draft that traced disputes back to the 19th century. Roosevelt rejected it. Having read the draft carefully, I agree that it was far weaker-it might even have put some congressmen to sleep if delivered in full. Still, a few details in it are worth mentioning. For example:
"In 1934, Japanese Minister of Foreign Affairs sent a friendly note to the United States stating that he firmly believed that no question existed between the two governments that was fundamentally incapable of friendly solution and that Japan had "no intention whatever to provoke or make trouble with any other power."
"We are fighting in self-defense; in defense of our freedom, of our liberties, and of our rights."
It also mentioned that Japsnese armed forces wounded, abused American citizens, sank American vessels, bombed American hospitals and schools, and crippled American business.
In reference to Japan’s actions in China and Indochina, the draft speech described them as "rapine, torture, massacre, and destruction."
Roosevelt's address was delivered at the Capitol shortly after noon on December 8, lasting seven minutes. That very afternoon, Congress almost unanimously voted to declare war on Japan, roughly 24 hours after the attack on Pearl Harbor.
Japan had clearly underestimated both America's capacity for rapid mobilization after provocation and its determination to enter the war. It had also misjudged the strength of US industrial production. Rather than delaying America's entry into the war as Japan had hoped, the surprise attack became one of its most fatal strategic miscalculations. The United States was not China in 1895, forced to endure humiliation and compromise after the Japan's surprise naval attack. Japan's ultimate defeat was foreshadowed the moment it made this unwise decision.
By now some friends may still question FDR had prior knowledge. Here I will share more discoveries after examining the Roosevelt archives.
As early as 1940, the United States had cracked Japan's diplomatic code, a breakthrough known as "Magic." Although translation capacity was limited, FDR, Hull, and top military leaders could obtain Japanese diplomatic intelligence quickly. However, Japan's military codes had not yet been broken before the Pearl Harbor attack. This meant that while US still faced a critical blind spot regarding Japan's military deployments and targets.
By late 1941, US–Japan negotiations had reached an impasse. In late November, Japan proposed a six-month "cooling-off period": the US would lift the oil embargo, and Japan would halt its expansion. Washington rejected this, and on November 26 demanded that Japan withdraw from China and Indochina, renounce its alliance with Germany and Italy, and refrain from attacking Southeast Asia in exchange for the lifting of the embargo.
On December 1, after learning of Japan's military buildup in Indochina, Roosevelt instructed the Secretary of State to request the Japanese diplomats in DC to inquire the Japanese Government "what the actual reasons may be for the steps already taken." He even handwritten a note: "because of the broad problem of American defense that I should like to know the intention of the Japanese government. (bottom right)"
Japan replied on December 5 that these were precautionary moves against Chinese troops. In discussions between Hull and the Japanese envoys, Japan suggested that if China and Japan entered peace talks, the US should immediately end its aid to China. Hull sharply retorted that he was reminded of Japan's aid to Hitler. The Japanese argued that the US viewed Japan's presence in Indochina as a threat, but from Japan's perspective, any other power occupying that region would also pose a threat. The meeting ended with mutual complaints about hostile press coverage in both countries. The two Japanese representatives then rose and left, "making the usual apologies for taking so much of the Secretary's time when he was busy."
On December 6, US intercepted a cable from Tokyo to its embassy in Washington, responding to the American proposal of November 26. At 9:30 that evening, US intelligence passed part of this cable to Roosevelt. After reading it, he told Hopkins that this meant war, likely an invasion of Southeast Asia. I believe this explains why, on December 7, he told Ambassador Hu Shih that war would come within 48 hours. He truly did not know that Pearl Harbor itself was the target.
Japan’s memorandum was originally scheduled to be delivered by its ambassador to Hull at 1 pm on December 7. But due to delays in translation at the Japanese Embassy, it was only presented at 2 pm-by which time Pearl Harbor had already been attacked. This amounted to launching war without declaration. The memorandum accused the US of having "failed to display in the slightest degree a spirit of reconciliation. The negotiation made no progress." It concluded that Japan "cannot but consider that it is impossible to reach an agreement through further negotiation."
What turned a war that might have been avoided into one that became inevitable? And what caused one nation's strategic miscalculation to evolve into a disaster for all of human civilization?
The lesson of Pearl Harbor is not only about vigilance against surprise, but also about the dangers of misjudgment and failure of dialogue. As we commemorate the 80th anniversary of the end of the WWII, let us remember not only the "day of infamy" itself, but also the broader truth it reveals: that peace is fragile, trust is precious, and the cost of miscalculation can be borne by generations. To honor history is not merely to look back with sorrow, but to look forward with wisdom-to ensure that the tragedies of yesterday do not become the inheritance of tomorrow.
