The advance into southern French Indochina in July 1941 invited the U.S. retaliatory measure of an oil embargo on Japan. To what extent did the Japanese political and military leaders at that time realize the danger?
The United States apparently issued warnings beforehand. The first was on July 21, three days after Japan sent the French Indochina authorities its ultimatum over the advance into southern French Indochina. On that day, U.S. Under Secretary of State Sumner Welles met with Kaname Wakasugi, Minister of the Japanese Embassy in Washington and special aide to Japanese Ambassador to the United States Kichisaburo Nomura, to try to stop Japan’s advance. The second was on July 23, after the authorities in French Indochina accepted Japanese troops’ advance into southern French Indochina. Welles met with Ambassador Nomura and put pressure on Japan by telling Nomura that it was impossible for the United States not to conclude that Japan was advancing to the southern Pacific regions for the purpose of military conquest.
On July 24, U.S. President Franklin D. Roosevelt invited Nomura to meet with him to propose that French Indochina should be treated as neutral territory while hinting, otherwise, at a possible oil embargo on Japan. Roosevelt told Nomura that he had so far made efforts to curb the calls in his country for an oil embargo on Japan because he believed it necessary for peace in the Pacific Ocean to give oil to Japan, but he would not be able to resist these calls much longer considering Japan’s advance into French Indochina.
Following the expansion of the Sino-Japanese War, the United States strengthened economic pressure on Japan. In January 1940, the United States had abrogated the U.S.-Japan Treaty of Commerce and Navigation and laid the groundwork for the president to impose an oil embargo. U.S. magazine Newsweek carried a story with the headline—“U.S. Has Japan Over Barrel With Lapse of Trade Treaty”—which read, “From now on the United States will be able to swing a big stick.”
In response to the Japanese military’s advance to northern French Indochina in September 1940, the United States decided on an embargo on exports of scrap iron to Japan. After that, the United States included important materials, such as copper and nickel, one after another onto the list of items of embargoed shipments to Japan. Although U.S. hard-liners against Japan demanded that the United States should impose an oil embargo on Japan, Roosevelt and U.S. Secretary of State Cordell Hull were carefully managing the situation. They fully understood that if the United States stopped exporting oil to Japan, whose self-sufficiency ratio of oil was less than 10 percent and who therefore depended on the United States, Japan would be driven into a corner.
Why did the United States react so strongly to the Japanese troops’advance into southern French Indochina? The reason is that the Dutch East Indies, Malaya and Burma under British control, and the Philippines under U.S. control, could be threatened directly by the Japanese military. On July 23, Hull told Welles, “The invasion of Southern Indo-China looks like Japan’s last step before jumping off for a full-scale attack in the Southwest Pacific.”
Nomura immediately sent a telegram to the Japanese Foreign Ministry that said the United States might impose an oil embargo on Japan.
But the Japanese government and the high command of the Army and Navy were optimistic that this would not happen. The Twentieth Group (War Coordination) of the Army General Staff wrote in its daily log on July 25, 1941, that it was convinced that if Japanese troops did no more than advance to French Indochina, the United States would not impose an oil embargo on Japan.
Also the diary, dated July 26, following the U.S. announcement to freeze Japanese assets in the United States on July 25, said that as the United States was sure to impose a total ban on exports to Japan, Lieutenant Colonel Arifumi Kumon, the Aviation Group chief, and Lieutenant Colonel Masanobu Tsuji, the Logistics Group chief of the Army General Staff’s Operations Bureau, strongly believed the southern expansion needed to be pushed through military means. The diary mentioned that the War Coordination Group did not expect the United States to impose a ban on exports to Japan for the time being and added that the United States would be forced to impose a total ban eventually, though not in that year or the following one.
Why were the Japanese military leaders doing nothing when faced with such a situation? The main reason was they mistakenly believed that the United States would allow Japan to advance up to French Indochina and Thailand. They thought that, as the Japanese troops had already advanced to northern French Indochina peacefully, the United States might not impose an oil embargo, which might directly trigger a war.
Prime Minister Konoe also did not predict that the United States would actually take retaliatory measures such as an embargo on oil exports.
According to a memoir written by former Foreign Minister Kijuro Shidehara, he understood that Konoe failed to predict the U.S. embargo, imposed two days after ships carrying Japanese soldiers set sail for southern French Indochina. Shidehara told Konoe flatly that this would escalate into a large war and pleaded desperately with Konoe to call the ships back to Japan. Konoe was very surprised at Shidehara’s approach and tried to reassure him that merely stationing soldiers would not lead to war.
Konoe placed high expectations on the Japan-U.S. negotiations between Nomura and Hull that were initiated in the spring of 1941 by the mediation of two U.S. Catholic clerics. In addition, an indirect reason for Konoe’s failure to foresee a strong U.S. posture toward Japan might have been that he was so absorbed by a political struggle when his Cabinet resigned in order to facilitate the removal of Foreign Minister Yosuke Matsuoka and replace him with Teijiro Toyoda.
Historian Ikuhiko Hata pointed out that the Japanese troops’ advance to southern French Indochina was to Britain and the United States like having a knife at their throats. He also said that it was difficult to treat it simply as a result of a vicious circle caused by an accumulation of errors and mutual distrust that is often seen in international politics.
After that, the high command of the Army and Navy argued that a drop of oil is equal to a drop of blood and urged the government to start a war early. The Twentieth Group of the Army General Staff wrote in a diary on July 26 that it did not expect a total U.S. ban on exports to Japan to happen. In the margin of the page of the diary, it was added in red ink that the judgment was wrong and the Army General Staff and the War Ministry were also wrong.
These earlier judgments proved fatal.