United States-Japan Relations During World War II

Reasons behind the Outbreak of the War between the United States and Japan

Primary Factors for the Aggravation of U.S.-Japan Relations

From a contemporary perspective, it is clear that the development of relations between the United States and Japan, which led to the outbreak of war between the two countries, was a very complicated process. According to O’Neill (2002), three primary factors influenced the aggravation of these relationships. First of all, America’s “open door” policy in China created significant tension with Japan due to the Japanese expansion in China (O’Neill, 2002). Second, the United States implemented economic pressure on Japan (O’Neill, 2002). And third, the series of events in the European theater of the war also impacted the acceleration of the Asian Crisis (O’Neill, 2002). The following sections will discuss particular aspects of the growing tension between the two countries.

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Japanese Expansion into China

These events cannot be properly understood without taking into account that China had been an important region for the global economy for a long time, and in the first half of the 20th century various colonial forces were interested in the economic potential of China (O’Neill, 2002). Another aspect that is important to consider is the role of Japan in the Asian region. Japan had been a “hermit kingdom” throughout its history, but since the 19th century, it had begun to expand in terms of political and economic power (O’Neill, 2002, p. 51). Accordingly, one of the primary regions of interest for Japan was China, where the United States had implemented an “open door” policy (O’Neill, 2002). This policy aimed to mediate the competition between different stakeholders, and thus it conflicted with the interests of Japan.

Japanese Aggression in China

Japan’s growing economic and political interest in the Chinese region inevitably led to the outbreak of military conflict (O’Neill, 2002). The first notable example of Japanese aggression in China was the invasion of Manchuria, nominally owned by China, in September 1931 (O’Neill, 2002). Because these actions provoked global concern, Secretary of State Henry L. Stimson decided to implement a policy of non-recognition, which aimed to isolate Japan politically by persuading other global powers to deny diplomatic recognition to Manchukuo (Japanese term for Manchuria) (O’Neill, 2002). However, in 1937, Japan decided to start “a full-scale invasion of China,” which included the Panay incident (O’Neill, 2002, p. 55). At this point in history, Japan became a significant threat to the Asian region.

New Order Declaration and Asian Crisis Acceleration

After the invasion in 1937, Japan occupied the majority of Chinese territories (O’Neill, 2002). Accordingly, in November 1938, Japan declared the creation of a “new order” in East Asia (O’Neill, 2002). The essential aspect of this policy was the closing of the “open door” policy, even though it was protested by many Americans. The main aim of the “new order” policy was to establish Japan as the economic and political leader in the Asian region and continue its domination (O’Neill, 2002). The United States responded with an unofficial sanction on aircraft and denial of credit to Japan (O’Neill, 2002). Also, American directly helped China by offering a $25 million loan (O’Neill, 2002). However, the Asian Crisis was accelerated by a series of events in the European war. In general, the impact of these events was that Germany’s military success in Europe weakened the position of most colonial powers that had interests in China (O’Neill, 2002). Therefore, Japan saw an opportunity for further expansion.

Economic Pressure and Road to War

The next step caused by the aggressive Japanese expansion was to isolate China economically and geopolitically by cutting ties between China and the outside world and demanding that Allied countries shut down their shipping of supplies to China (O’Neill, 2002). The United States responded by declaring an embargo on aviation fuel and some metals on 25 July 1940. Also, America sent the Pacific Fleet to Pearl Harbor. The tension continuously grew as Japan signed the Tripartite Pact with Germany and Italy in September 1940 in an attempt to mitigate the threat posed by the United States. Additionally, Japan started to plan the invasion of Indochina, aiming to take greater control over Southeast Asia. The response of the American government was immediate, as in September 1940 the conditions of the embargo were made more severe by adding steel to the list of goods banned from trade with Japan.

Pearl Harbor and the Outbreak of the War

In July 1941, Japan moved troops to southern Indochina. At this point, the prevalent opinion among the citizens of the United States as well as the majority of political stakeholders was that Japan represented a significant threat to America and should be stopped. Negotiations on freezing the current situation in China did not have a strong influence on the development of the conflict as the United States government learned about Japan’s plans that were about to be set in motion on 25 November 1941 (O’Neill, 2002). Subsequently, on 7 December 1941, Pearl Harbor was attacked, and the United States entered World War II.

The Revision of the Neutrality Acts as the Path of America’s Involvement in World War II

The United States Policies toward War

The goal of this essay is to investigate how American foreign policy before World War II was influenced by the experience of involvement in World War I. It is also essential to identify the factors that had a primary impact on the entrance of America into World War II even though the American government did not initially plan to enter the war. It is possible to identify two primary stages in the development of policies leading up to the war: before the outbreak of World War II, and during the beginning of the war from 1939-1941.

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O’Neill (2002) states that, due to the historical peculiarities of the establishment and development of the United States as a country, isolationism appears to be one of the prevailing ideas in the American political paradigm. Primarily, the policy is determined by its geographical location, as the country is naturally separated from Europe. It should also be mentioned that the policy of isolationism was reinforced by the involvement of the United States in World War I, which had numerous negative consequences for the country, primarily in terms of economic burden and casualties. Therefore, in the decade before World War II, the U.S. Congress considered the balance of power in the world to be irrelevant for the United States and implemented a policy of isolationism.

Avoiding the Mistakes of World War I

As previously mentioned, the prevailing climate of public opinion concerning foreign policy was significantly influenced by the experience of World War I. The primary and most evident embodiment of this social and political climate is the series of four Neutrality Acts, which were passed between 1935 and 1939. In general, these acts were based on the idea that involvement in any war would have significant negative consequences for America, and thus they should be avoided.

The provisions of these acts were largely based on the avoidance of the factors that were, according to the views expressed by members of Congress, the initial reasons that led the United States into World War I. In particular, the Neutrality Acts included the following aspects. The provisions of these acts banned such activities as “giving loans and credits to belligerents” as well as shipping arms, weapons, and other ammunition to them (O’Neill, 2002, p. 15). Also, the Neutrality Acts banned American citizens from traveling on belligerent ships and vessels along with arming American merchant ships. In contrast, non-military trade was largely supported by Congress. Thus it is generally valid to state that the American government was not interested in involvement in any military conflict. However, from a modern perspective, it is evident that these policies were only beneficial in the short term.

Arsenal of Democracy”

Even though isolationism was the prevailing political opinion in the United States, there was a continuously growing awareness of the threat represented by the Nazis in Germany as well as by Japanese economic and political ambitions (O’Neill, 2002). By 1938, America had acquired an understanding of the importance of preparing for the upcoming military conflict in Europe. Primarily, this preparation process was initiated and largely promoted by Franklin Roosevelt, whose election to a third term in 1940 was one of the most influential factors in terms of America’s further involvement in World War II.

Nevertheless, Roosevelt was not willing to enter the war openly. Instead, he promoted a policy of military support for U.S. allies, which was known as the “Arsenal of Democracy.” Several activities were enacted to support the allies. In November 1939, the American government revised its cash and carry a policy to trade arms to Britain. In September 1940, the Destroyers for Bases Agreement was signed with Britain. Finally, the Lend-Lease Act made the United States a non-fighting, yet fully supportive ally of Britain. Each of these actions represented an additional deviation from the policy of isolationism and neutrality, and Roosevelt was widely criticized for them. As the United States became allied with Britain, America’s involvement in World War II was inevitable.

Drift toward War in Atlantic

As was mentioned previously, numerous factors contributed to the United States’ entering the war (for example, the growing tension in its relations with Japan). The year 1941 saw the logical conclusion of Roosevelt’s policies of the prior decade toward war. The series of violent encounters between U.S. Navy escorts and German naval forces, most notably in September and October, was the primary reason for the repeal of the neutrality restrictions on November 13. Arming U.S. merchant ships made it possible to carrying cargo to Britain through the war zone, and thus the United States became an active participant in World War II. Based on the factors mentioned here and their underlying causes, it is possible to state that America’s involvement in the war was inevitable.


O’Neill, W. L. (2002). A democracy at war: America’s fight at home and abroad in World War II. Cambridge, MA: Harvard University Press.

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