The neutrality acts of the late 1930s sharply restricted the export of U.S. arms and strategic materials to warring nations. For example, the Neutrality Act of 1937 allowed nations, at the discretion of the President, to acquire any items except arms from the United States, provided that they immediately paid for such items and carried them on non-U.S. ships. This “cash-and-carry” policy was engineered by President Franklin Roosevelt to assist Great Britain and France in their fight against Hitler’s Germany. Roosevelt did grant an exception that allowed British ships to carry U.S. weapons to China.

The military used its power to dominate government agencies and citizens. Perhaps the most important factor that enabled the military dominance, however, was grassroots militarism. The glorifying of war dead and promotion of selfless sacrifice, coupled with fear of social ostracism, served as powerful motives for otherwise unwilling people to support the war effort.

Tensions had been building for years between the U.S. and Japan, which relied heavily on imports of American oil and steel. Even before World War I (when the U.S. and Japan were allies), the two nations emerged as rival powers in the Pacific. In the 1930s, Japan’s imperialist expansion and the rise to power of its militarist exacerbated the rift. The United States, seeing to curb those ambitions, embargoes shipments to Japan of aircraft, scrap metal, iron ore and steel, and oil.

In September 1940, Japan signed the Tripartite Pact with Germany and Italy and invaded French Indochina. A few months later, Japan and Russia signed a non-aggression treaty, removing the Soviet Union as an obstacle to Japanese expansion in Asia. In July 1941, Roosevelt froze all Japanese assets in the United States. Negotiations between the U.S. and Japan continued with no progress.

Japan regarded American sanctions, especially the oil embargo, as a threat to its war effort in China and to the survival of the Japanese Empire.

By 1940, America faced a double threat overseas. Bent on controlling much of Asia, Japan threatened America’s economic interests there and its long-standing relationships with the Philippines and China. German forces had swept across Europe and were now attacking America’s close ally Great Britain.

Germany, Italy and Japan had signed an alliance, sparking fears of worldwide conquest by these three Axis powers. With Germany on one side and Japan on the other, U.S. Senator Claude Pepper fumed that “the vast pincer movement begins to crush us between its two jaws.”

The U.S Pacific Fleet’s relocation to Hawaiian waters brings conflicting reactions. Is it a restraint on Japan or creating a vulnerable target? President Roosevelt told Admiral James O. Richardson, Commander-in-Chief of the U.S. Pacific Fleet that retaining the fleet in Hawaiian waters after it concluded large-scale maneuvers in the spring of 1940 would “exercise a restraining influence on the actions of Japan.”