After Japan’s resignation from the League of Nations tensions only began to increase in the international community. A series of declarations of superiority and independence by Japan would put the Pacific Empire in the United States’ warning list. It would be in 1937 along with such atrocities as the Rape of Nanking when the United States would officially begin condemning Japan.
In 1937 a full-scale war between Japan and China would break out beginning at the Marco Polo Bridge. Japan had been carrying out intensive military operations near this bordering bridge antagonizing the Chinese leading to the fatal shooting of a Japanese soldier. Japan’s beginning of full-on antagonistic actions would not go unnoticed by the United States
At the end of 1937 one of the worse atrocities of Japanese aggression occurred in the Chinese city of Nanking. After Japanese capture of the city a at the very least tens of thousands of Chinese were raped and murdered by the Imperial Japanese Army.
US President Franklin Delano Roosevelt set to enact harmful economic laws against Japan by 1940. Beginning with the Export Control Act which banned US shipment of airplane parts and fuel to Japan. The act was labeled the “Moral Embargo” criticizing Japan’s actions taken against the Chinese.
When Japan invaded French-controlled Indochina in 1940 the United States furthered its “Moral Embargo” by expanding the restrictions to scrap metal. Along with these restrictions the United States also closed the Panama Canal to the Japanese effectively cutting off an efficient trade route from the Atlantic Ocean.
Continuing failed peace negotiations mediated by the United States only led to further embargoes. The refusal of a peace treaty in 1941 by General Tojo led the US to ban shipments of oil to Japan. Oil being one of Japan’s most crucial imports to fuel their expansive Navy and Air Force.
The US Oil Embargo only led Japan to seek for different means to acquire their fuel. The Dutch East Indies had a quantity large enough to warrant a Japanese invasion. However to expand to this area Japan would need to invade the Philippines, a US territory.
The final peace negotiation between the US and Japan was sent in November 1941 by Secretary of State Cordell Hull. The Hull Note was considered an ultimatum from the US giving little to no room for Japan to keep anything from accepting this negotiation. All peace talks stopped between the two Pacific Nations after the delivery of this note.
Before the attack on Pearl Harbor Japan drafted a 14 page encrypted message with this Type 97 Crytography Machine called PURPLE, detailing Japan’s plan to begin war. Due to the complexity of the encryption however the United States was not able to decipher the declaration of war until hours after the attack on Pearl Harbor.