By June 1939 Japan was deeply entrenched in China with a military stalemate, the Chinese willing to fight a war of attrition, and there was no political settlement in sight. Japan had just suffered a major defeat at Nomonhan, though this was not fully appreciated in Washington at the time, and elements of Japanese leadership were increasingly suspicious of Western intentions. That same month the U.S. formally notified Japan it would terminate the 1911 Treaty of Commerce and Navigation, effective January 1940. This did not impose sanctions immediately but freed the U.S. legally to restrict trade later. The purpose of the actions was to signal displeasure with Japan’s conduct in China, create leverage without escalation, and preserve diplomatic ambiguity. It was not well received in Japan as they understood that beginning in January 1940 there would be no treaty in place that could limit trade restrictions. At the same time the State Department issued nonbinding requests to U.S. firms not to sell aircraft, aviation fuel or strategic materials to Japan. This reflected Hull’s belief that economic pressure should precede coercion, and coercion should precede war. This would come to be known as the “moral embargoes” and marked the first move from moral pressure towards economic leverage

French Indochina

A key reason China could continue fighting was that foreign supply routes remained open, especially the Burma Road and rail and port access through French Indochina, particularly via Haiphong into Yunnan Province.From Tokyo’s perspective, cutting these supply lines became essential. Japan was presented a strategic opportunity with the collapse of France to German forces in June 1940. As a consequence the Vichy regime replaced the French government. This left French colonial authorities isolated, under-resourced, and politically uncertain. To Japanese planners, Indochina now looked militarily weak and diplomatically unsupported and unlikely to receive British or American military support in the short term. To the Army, Navy, and politicians this created a low-risk window of opportunity.

Japan initially pursued its objectives through coercive diplomacy, not outright invasion. Japan demanded that Vichy France close supply routes to China, permit the Japanese to station inspectors at transportation junctions (and later military forces), and provide unfettered access to airfields in the North. Vichy France wanted to preserve sovereignty but lacked the military means to resist and so hoped that accommodation would prevent full occupation. Negotiations dragged on while Japan prepared militarily, a familiar pattern since Mukden.

Despite French promises, Japan believed that supplies were still leaking into China, French officials were unreliable, and only physical control could guarantee closure of routes. The Japanese Army argued that diplomatic assurances were meaningless without troops on the ground, reflecting the Army’s broader pattern of fait accompli strategy.

In September 1940, Japanese forces crossed into northern Indochina and occupied key airfields and rail lines. They clashed briefly with French colonial troops but soon enough all resistance collapsed. Shortly afterward a formal agreement legalized the Japanese presence while French administration remained nominally in place.  Japan was fine with leaving administration to the French because they had gained what they wanted: control of transport corridors and air bases from which to control supplies into China.

Japan limited itself initially to northern Indochina because the stated goal was cutting China’s supply lines and it allowed Japan to test Western reactions in an incremental way as it avoided directly threatening oil supplies.

To the international community, Japan deliberately framed this as a “temporary” measure, a defensive necessity and not an annexation. But while China was the immediate justification, larger strategic calculations were at work. After the defeat at Nomonhan, the Northern expansion against the USSR lost credibility and attention shifted south toward Southeast Asia. Indochina offered a stepping stone toward the Dutch East Indies with airfields within reach of British Malaya. Japan also believed a decisive move would demonstrate resolve to the point the U.S. and Britain would protest but would not fight or take any decisive action. Internally it provided prestige to the military and the government and was promoted at home. Japan calculated that in the short term Britain was fully engaged in a battle for its national life (the “Battle of Britain”) while the U.S. was still divided and formally neutral.

The U.S. response was as Japan expected: a strong diplomatic protest, limited export controls, but no other embargo action. All in all, this reinforced Japanese beliefs that incremental expansion would work.

Reaction with the U.S. Government

The U.S. response to Japan’s occupation of northern Indochina exposed deep internal divisions within the Roosevelt administration over how far and how fast to confront Japan. At the center of the debate was a shared recognition that Japan had crossed an important threshold, but no consensus on whether that threshold justified decisive economic retaliation or continued diplomatic caution.

Within the State Department, Secretary of State Cordell Hull favored a measured, incremental response. Hull believed Japan’s move was aggressive but still reversible and that premature, sweeping sanctions, especially on oil, risked provoking a war the United States was not yet prepared to fight. State Department officials continued to emphasize negotiation, the preservation of legal and moral principles (such as the Open Door in China), and the use of graduated economic pressure to influence Japanese decision-making. Hull and his advisers, especially Ambassador Grew, held out hope that divisions within Japan, particularly between civilian moderates and the military, could still be exploited diplomatically.

By contrast, Treasury Secretary Henry Morgenthau Jr., supported by some in the Interior and Navy Departments, argued that Japan’s occupation demonstrated that incremental pressure had failed; it had been applied for almost three years. This faction favored stronger economic sanctions, including tighter export controls and financial restrictions, to signal that further expansion would carry unacceptable costs. Morgenthau was particularly concerned that continued U.S. trade, especially in oil, gasoline, aviation fuel,  and scrap metal, was materially enabling Japanese aggression. President Franklin Roosevelt ultimately sided, for the moment, with Hull’s caution: the U.S. imposed new export controls and intensified diplomatic protests but stopped short of an oil embargo. The compromise reflected a broader strategic judgment that time was needed to strengthen U.S. defenses while keeping open the possibility, however slim, of restraining Japan without war.

Export Controls Act 

In July 1940 Congress passed the Export Controls Act in response to Japan’s move into northern French Indochina. At the core of the legislation was that the State Department gained authority to license or deny exports. Immediately restrictions were placed on aviation gasoline, high quality scrap iron and machine tools. The licensing process gave the State Department the ability to “approve” the request and then slow march the license through the administrative process where decisions were deliberately incremental and often reversed

The Departments of Treasury and Interior wanted stronger measures and more excluded items. Despite pressure from Treasury and some Navy officials, the administration deliberately excluded oil from the provisions of the 1940 Act. Petroleum exports continued, ordinary commercial goods remained largely unaffected, and financial transactions were not yet frozen. All this reflected Secretary Hull’s view that an oil embargo would be indistinguishable from a declaration of economic war. This marked a clear escalation in U.S. policy, but one carefully calibrated to apply pressure without forcing an immediate showdown.

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archive

In the summer of 1939 Japan was increasingly bogged down in combat with China. As you can see in the map below, Japan controlled not only Manchukuo (Manchuria) but swaths of Inner Mongolia and China. Importantly, Japan also controlled almost all major seaports facing the East and South China Sea. Manchukuo presented its own control issues, largely centered around rampant banditry, but all the other areas required the Kwantung Army (Imperial Japanese Army on the mainland) to provide occupation and policing forces in areas they had conquered. At the same time the Kwantung Army continued offensive operations in Northern China.

Notice that Japan also had an extensive border with the Soviet Union as well as a history of conflict with czarist Russia that extended some 60 years back in time including the 1904-1905 Russo-Japanese War which removed Russian presence in Manchuria and Korea. Russia lost the warm water ports in Darien and Port Arthur, access to the resources of Manchuria, and was often required to transport goods and resources via the Trans-Siberian Railway rather than via ship. In addition Russia was required to cede the lower half of Shanklin Island (just north of Japan). All of this fit into Japan’s “strategic buffer” concept keeping China and Russia/Soviet Union at “arm’s length” from the home islands.

The Nomonhan Incident

Also known as the Battles of Khalkhin Gol, the Nomonhan Incident was a major but undeclared border war fought between Imperial Japan and the Soviet Union’s Mongolian forces from May to September 1939. It occurred along the poorly defined frontier between Japanese-controlled Manchukuo and Soviet-aligned Mongolia. Though officially termed an “incident” by Japan to avoid acknowledging a formal war, the conflict involved tens of thousands of troops, armor, artillery, and aircraft, making it the largest land battle Japan fought before the Pacific War. The fighting ended in a decisive Soviet victory, delivering a shock to the Japanese military and reshaping Japan’s strategic direction on the eve of World War II.

The Background

At the root of the conflict was a disputed, ambiguous border. Japan claimed the boundary lay along the Khalkhin Gol (Halha River), while the Soviets and Mongolians insisted it lay several miles east. The area was remote, sparsely populated, and economically marginal but symbolically important as a test of sovereignty and power. It was also extremely remote from the Imperial Japanese Army (IJA) Staff and Ministry in Tokyo. All of this was simply ingredients of a toxic stew only awaiting the flame to start a boil. And the Kwantung Army was only too happy to ignite the flame.

The Kwantung Army had a well earned reputation for acting autonomously from Tokyo, initiating aggressive actions to force what it believed were the necessary political outcomes, and viewing itself as the vanguard of Japan’s continental destiny. This attitude led to the Mukden Incident (1931), the Marco Polo Bridge Incident (1937), and the quagmire of the Second Sino-Japanese War. By the summer of 1939 the IJA was already stretched thin, had terrible logistics support, and was lacking in combined arms capability – meaning tanks, artillery and ground support from aviation assets. Financially, Japan was stretched thin in trying to keep the IJA funded at the same time funding the Navy’s capital intensive shipbuilding efforts.

Nonetheless, by 1939 the bane of IJA’s existence – an independent, insubordinate junior officer corps believed that controlled escalation against the Soviets could secure Japan’s northern frontier, expand the strategic buffer or even open the door to expansion into resource-rich areas of Siberia. In the view of Japan, the majority of the peoples in Siberia and Mongolia were Asiatic and thus properly best served under the Imperial Protection of the Emperor. They did not bother to ask the people of those areas about their preference.

Northern Expansion Doctrine (Hokushin-ron)

Within Japan’s strategic debates, the Army strongly favored Hokushin-ron, the idea that Japan’s future lay in expanding northward against Russia rather than southward into Southeast Asia. This belief rested on overconfidence from victories in China, an underestimation of Soviet military modernization, and a deep seated anti-communism which was, at this time, being suppressed in the home islands. Nomonhan emerged from a belief that the Red Army could be tested, pressured, and defeated through limited engagement. It was less a grand strategy and more a tactical escalation.

In part it was also pushing back on the evolving southern expansion doctrine being proposed by the Imperial Japanese Navy (IJN) whose interest lay in the resource-rich Southwestern Pacific, especially the oil fields of Borneo, Malay and Java.

The local IJA commanders were confident that Japanese infantry superiority would compensate for weaknesses in armor and logistics. In addition, they believed that the Soviets would avoid a major escalation. The Kwantung Army assumed that a sharp, localized victory would strengthen Japan’s hand diplomatically and militarily.

The IJA horribly misread Soviet intentions. The Soviets retained the memory of the humiliating defeat by Japan of czarist Russia. It was a lingering shame that the Soviets would never let happen again. They were more than willing to fight. They also had superior tanks and artillery and a capacity for combined arms operations with their ground forces. Japan also failed to recognize that the Soviets had the same essential “strategic buffer” view as Japan. Mongolia as part of that buffer and the Soviets would respond decisively to any threat in that region.

Combat

In the period May–June 1939, the initial clashes involved cavalry and infantry skirmishes for small areas of land as well as an island in the middle of the border river. Japanese forces crossed into disputed territory, driving out Mongolian units. Early successes reinforced Japanese confidence.

In June, the Soviets appointed General Georgy Zhukov to command. Zhukov rose to prominence with his leadership at Nomonhan. He was a brilliant tactician and field commander later becoming the most prominent and successful Soviet military commander during World War II often credited as the key strategist behind major Eastern Front victories against Nazi Germany. He rose to the position as Chief of the General Staff and a Marshal of the Soviet Union, leading the defenses of Moscow, Leningrad, Stalingrad and commanding the final assault on Berlin. He was formidable. 

Long story, told short, Zhukov prepared a coordinated counteroffensive rather than piecemeal retaliation, amassing artillery, tanks, and aircraft supported by secure logistics/supply lines. In late August, Zhukov launched a classic double-envelopment, using tanks and mechanized infantry to encircle Japanese forces who lacked effective anti-tank weapons, were undersupplied, and relied on infantry assaults against armor. The result was catastrophic. Entire Japanese formations were destroyed or rendered combat-ineffective. It was a clear battlefield defeat involving some 20,000 Japanese casualties with the loss of experienced officers and elite units. Japan agreed to a ceasefire in September 1939, restoring the status quo but psychologically, the damage was done. It was the first unequivocal defeat suffered by Imperial Japan since the Meiji era.

Unintended Consequences

Nomonhan should have shattered Japanese assumptions – but it did not. Japan continued to believe that Japanese fighting spirit and bushido were enough to triumph and could overcome material inferiority and weak logistics. This would plague them all the way through 1945. They also continued to believe that wars could be tightly controlled and limited.

The defeat decisively undermined the Northern Expansion faction within the Army. After 1939 all plans for war against the Soviets were shelved, a defensive posture was adopted along the Manchurian frontier, and Japan avoided conflict with the Soviets for the remainder of WWII. This shift paved the way for Nanshin-ron (southern expansion), pushing Japan toward Southeast Asia and the Dutch East Indies’ oil. It was the path to confrontation with Western colonial powers. In this sense, Nomonhan helped set Japan on the road toward Pearl Harbor.

Perhaps the most profound unintended consequence was for the Soviet Union. Stalin gained confidence that Japan would not attack in the east and soon enough the two nations signed the Soviet–Japanese Neutrality Pact (1941) allowing Soviet divisions to later be transferred west to defend Moscow against Germany. The Nomonhan incident influenced the outcome of the European war, not just Asian geopolitics.

The Nomonhan Incident stands as a warning ignored about the limits of aggression driven by ideology rather than sound political and military strategy and tactics. It revealed the dangers Clausewitz warned of: wars initiated for political symbolism without a clear path to decisive victory would ultimately end in disaster for those who initiated the action.

Nomonhan was not merely a border clash. It was Japan’s strategic crossroads. Historians have come to now recognize Nomonhan as one of the most consequential “incidents” of the twentieth century – even though it largely remains unknown in the West.

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archives. | Pacific area map of 1939 courtesy of MapWorks via Wikipedia Commons.

After the Marco Polo Bridge Incident (July 1937)  the United States took measured but meaningful actions in support of China, while still stopping well short of alliance or military intervention. The pattern is best described as moral, diplomatic, and limited material support, shaped and heavily limited by existing U.S. neutrality laws and the general sense of isolationism among the American people and Congress.

Given the mood and legal constraints facing the Roosevelt administration there was little to be done if the goal was to avoid military actions. What actions were taken are best described as nonrecognition and positioning. To that end the U.S. refused to recognize Japanese territorial gains in China, continued to uphold and advocate the Open Door Policy regarding commercial trade with China, and treated China as the legitimate sovereign power throughout the conflict.

This stance mattered because it denied Japan international legitimacy as virtually all nations followed the U.S. lead in this matter. It also gave China an enhanced standing in international diplomatic forums. The actions, limited as they were, did signal U.S. sympathy without military commitment. While Secretary Cordell Hull worked the diplomatic world, striking a balance that applied limited international pressure in a moral sense to Japan, he also had to temper calls from Britain for concrete economic sanctions. Britain was at the threshold of war in Europe (which began September 1939) and was concerned with Japanese aggression in the Asia Pacific area against British colonies and interests.

A Divided Asian Policy

In the post “American Diplomacy in 1937” we considered some of the key figures in determining the U.S. diplomatic response to Japanese aggression in China: President Franklin D. Roosevelt; Cordell Hull, Secretary of State; Stanley Hornbeck who headed the Far East Department; Nelson Johnson, Ambassador to China; Joseph Drew, Ambassador to Japan; and key advisors to Hull – J. Pierpoint Moffat and Hugh Wilson. Moffat was the son-in-law of Joseph Drew. Wilson had served in Japan in the mid-1920s.

Roosevelt, Hornbeck and Johnson can be viewed as members of an “activist camp” although in varying degrees. Hull, Grew, Moffat and Wilson would be viewed as members of a “don’t aggravate Japan” camp who wanted to confine U.S. responses to diplomatic channels while avoiding economic sanctions of any form as well as military action. At this point “military action” primarily meant action by naval and marines forces stationed in Shanghai as protection of U.S. citizens and interest in Shanghai’s International Settlement as well as citizens and interests upstream on the Yangtze River.

Hull’s position was to do nothing to antagonize Japan but nothing to assist them either. President Roosevelt did not like Hull’s Asian policy. While he accepted them as prudent the President was frustrated by a policy that let Japan get away with blatant aggression. Roosevelt was known to keep his own counsel and on occasion “go his own way.” In October 1937 he gave what came to be known as the Quarantine Speech that implicitly condemned Japan’s aggression (alongside Italy and Germany). In the speech he framed Japan as a disturber of international order but deliberately avoided naming Japan to prevent escalation. But his meaning was clear: “The present reign of terror and international lawlessness… [means that] the very foundations of civilization are seriously threatened…international anarchy destroys every foundation of peace…This situation is of universal concern.” Roosevelt went on to compare the terror and lawlessness to a contagion becoming an epidemic and note that the only reaction to an epidemic is quarantine. “War is a contagion, whether it be declared or undeclared…There must be positive endeavors to preserve peace.”

The speech did everything that Hull was trying to avoid. First, it exacerbated diplomatic relations with Japan. Although Roosevelt never named Japan, Japanese leaders and the press immediately understood that Japan was one of the principal targets. From Tokyo’s perspective, the speech signaled that the United States was morally siding with China, Japan was being described as a threat to international order, not merely a regional power pursuing interests, U.S. neutrality was becoming conditional rather than detached, and this signaled a shift from U.S. disapproval to U.S. warning.

The Japanese Foreign Ministry responded with measured, non-confrontational statements. This restraint reflected a desire to avoid provoking sanctions, an awareness that Japan still depended heavily on U.S. trade, and a hope that American isolationism would reassert itself. In the Cabinet it was viewed as a trial balloon for later economic sanctions. Within the military it added to the view that the U.S. viewed them as a second-rate nation. The Japanese Army dismissed it as moralizing. Within the Navy the speech confirmed fears that American opinion was shifting and that the current moral pressure could evolve into economic or naval measures – but still considered armed conflict years away.

Hull was also concerned that the speech would have the western signatories to the Nine Power Treaty call for an international conference (which it did) and that the U.S. would be thrust into the leadership role. Within domestic politics/policy it marked the beginning of a division within the nation’s foreign policy with Roosevelt pushing for something more dynamic and assertive – and yet not giving any concrete substance to the notion – while at the same time Hull was trying to maintain the established policy. 

This difference would prove to be somewhat problematic as Roosevelt tended to think in broad, sweeping terms while avoiding detailed plans. Hull tended to think in categories of fundamental goals without incremental steps towards that end.

Proposals and Next Steps

Among the activists, Hornbeck shared Hull’s conviction that diplomatically Japan was not an honest dialogue partner, but also understood Japan’s foundational interests: economic and political security in her area of interest. While much of the U.S. Department of State believed Japan had “taken on more than it could chew,” Hornbeck understood that with every bite, Japan’s appetite increased, but that there were very different levels of “appetites” between the nationalist/militarists in Japan and their moderate counterparts in civil governance and diplomacy. Hornbeck wanted to actively approach Japan with the “carrot” that would give them the security they desired, but needed a “stick” to forestall further Japanese aggression in China. In this he was aligned with President Roosevelt, but the President in 1937 did not believe he had the support of either Congress or the public for any form of “carrot.”

While the U.S. internal debates continued and Japan aggressively moved in China, an element of the Japanese government initiated “feelers” from offices in Tokyo, Washington DC, and Paris. They wanted to see if the U.S. would help present Japan’s terms for peace and moderate Sino-Japanese talks. Unfortunately, Japan’s offer matched their history of vague diplomacy, asking for specific current actions from China while pinning their commitments to future events that might or might not happen. Ambassador Grew in Japan, in general more positive about Japan than others, acknowledged that his analysis of the terms to China were really full capitulation couched in ambiguous language. Grew attempted to get Japan to commit to “details” consistent with the Nine Nations Treaty of which Japan was a signatory. Eventually the initiative “died on the vine.”

By December 1937, Treasury Secretary Morgenthau, of a like mind with Roosevlet and Hull, raised the possibility of beginning to seize Japanese assets held in the U.S. as a first step. Roosevelt was initially keen on the idea, but by late January 1938 that initiative “died on the vine.”

There were other initiatives but in the end all suffered the same fate. The U.S. was not able to field a policy for Japan other than Hull’s “don’t aggravate, just wait.” Some of the division and lack of action was certainly tied to U.S. politics with the American people largely isolationists, still suffering from effects of the Great Depression, and mid-term elections being close by. But a good deal was connected to the divisions with the State Department.  Ambassador Grew, long serving in Japan, had a belief in the moderates of the party – people he had known since the 1920s. Historians agree that he placed too much emphasis on the standings of the moderates, who by the 1930s were largely sidelined.  With Washington DC, the Far East Department (FED) firmly believed that the nationalists and military elements held key control of Japan’s policies. FED believed that Japan had not only regional but global aspirations and foresaw in the spring of 1938 that Japan would formally partner with Germany and Italy – which they did in the September 1940 Tripartite Treaty.

By the Spring of 1938, China was holding its own…to some degree. Hull concluded that Japan was overextended, lacked the resources to capture China, much less control China, and concluded that Japan would never win the war. And that they might even lose the war over time. This “betwixt-and-between” view was supported by General Joseph Stillwell, US Army, an advisor to Chiang Kai-shek.  The next effect was to further convince Hull that his policy of waiting while not aggravating Japan was the right course of action.

As a result, a routine was established:  Japan took some action which required Ambassador Grew to protest. Japan offered conciliatory words with no concrete actions apart from a renewed request for the U.S. to moderate peace talks (as before). In the end, with no actions forthcoming, the U.S. would formally protest. Japan did not respond.  It was a cycle of rinse and repeat as each incident came along.

In May 1938, Japan initiated a campaign of strategic bombing of Chinese civilian populations. This campaign was extensively covered by U.S. news outlets and American missionaries. At the movies, new reels and reports of the campaign were seen by the American public. It is estimated that in 1938, in urban America, the average adult saw two movies in-theatre each week. It did not take long for a wave of public outcry to arise. From that came the calls for U.S. companies to stop their “blood trade” with Japan. The outcry forced Hull to initiate a “moral embargo” asking U.S. companies to voluntarily stop trade with Japan in aircraft, aviation maintenance items, aviation fuel, and key resources and tools needed for the production of war goods. Hull’s goal was to calm the U.S. public.  At the same time Hornbeck and other departments in State wanted the U.S. to abrogate the 1911 U.S.-Japan Trade Agreement.

The war in China continued through the summer and into the autumn. The Chinese lost the city Xuzhou at the end of May but the battle proved the Chinese strategy of attrition that increasingly made Japan pay an ever increasing costs in terms of casualties and equipment. The Japanese were drawn into the Battle of Wuhan which involved over 1 million soldiers and great loss, but marked the end of Japan’s rapid advance and the beginning of a long-term strategic stalemate. This advance was also forestalled when Chinese forces breached the dikes of Yangtze River, creating a massive, man-made flood to block the Japanese advance.

In November 1938, the Prime Minister of Japan, Prince Konoe, gave what is called the “New Order” speech that made public what the Far East Department (FED) had long promoted – Japan’s ambitions were super regional and also global. This was the start of a coming change within the State Department, the Treasury Department and Congress to make loans to China and begin to discuss abrogating the 1911 U.S.-Japan trade agreement. Withdrawing from this agreement made later sanctions and embargoes possible.

Of interest is also at this time, Ambassador Grew was vacationing in the United States, and when asked the Charge of Affairs Doorman reported that the military and nationalists were in complete control of the governance of Japan. This March 1939.

Image credit: various photographs from Naval Aviation Museum, National World War II Museum, and US Navy Archive