[This talk was the Arthur M. Krolman Lecture at the 30th Anniversary Supporters Summit of the Ludwig von Mises Institute, Callaway Gardens, Georgia, on October 26, 2012. Click here to watch the video of this talk.]Many people are misled by formalities. They assume, for example, that the United States went to war against Germany and Japan only after its declarations of war against these nations in December 1941. In truth, the United States had been at war for a long time before making these declarations. Its war making took a variety of forms. For example, the U.S. navy conducted "shoot [Germans] on sight" convoys - convoys that might include British ships — in the North Atlantic along the greater part the shipping route from the United States to Great Britain, even though German U-boats had orders to refrain (and did refrain) from initiating attacks on U.S. shipping. The United States and Great Britain entered into arrangements to pool intelligence, combine weapons development, test military equipment jointly, and undertake other forms of war-related cooperation. The U.S. military actively cooperated with the British military in combat operations against the Germans, for example, by alerting the British navy of aerial or marine sightings of German submarines, which the British then attacked. The U.S. government undertook in countless ways to provide military and other supplies and assistance to the British, the French, and the Soviets, who were fighting the Germans. The U.S. government also provided military and other supplies and assistance, including warplanes and pilots, to the Chinese, who were at war with Japan. The U.S. military actively engaged in planning with the British, the British Commonwealth countries, and the Dutch East Indies for future combined combat operations against Japan. Most important, the U.S. government engaged in a series of increasingly stringent economic warfare measures that pushed the Japanese into a predicament that U.S. authorities well understood would probably provoke them to attack U.S. territories and forces in the Pacific region in a quest to secure essential raw materials that the Americans, British, and Dutch (government in exile) had embargoed. 
Consider these summary statements by George Victor, by no means a Roosevelt basher, in his well documented book The Pearl Harbor Myth.
Roosevelt had already led the United States into war with Germany in the spring of 1941—into a shooting war on a small scale. From then on, he gradually increased U.S. military participation. Japan's attack on December 7 enabled him to increase it further and to obtain a war declaration. Pearl Harbor is more fully accounted for as the end of a long chain of events, with the U.S. contribution reflecting a strategy formulated after France fell. . . . In the eyes of Roosevelt and his advisers, the measures taken early in 1941 justified a German declaration of war on the United States—a declaration that did not come, to their disappointment. . . . Roosevelt told his ambassador to France, William Bullitt, that U.S. entry into war against Germany was certain but must wait for an "incident," which he was "confident that the Germans would give us." . . . Establishing a record in which the enemy fired the first shot was a theme that ran through Roosevelt's tactics. . . . He seems [eventually] to have concluded—correctly as it turned out—that Japan would be easier to provoke into a major attack on the Unites States than Germany would be.  As Secretary of War Henry Stimson testified after the war, "we needed the Japanese to commit the first overt act." 
The claim that Japan attacked the United States without provocation was . . . typical rhetoric. It worked because the public did not know that the administration had expected Japan to respond with war to anti-Japanese measures it had taken in July 1941. . . . Expecting to lose a war with the United States—and lose it disastrously—Japan's leaders had tried with growing desperation to negotiate. On this point, most historians have long agreed. Meanwhile, evidence has come out that Roosevelt and Hull persistently refused to negotiate. . . . Japan . . . offered compromises and concessions, which the United States countered with increasing demands. . . . It was after learning of Japan's decision to go to war with the United States if the talks "break down" that Roosevelt decided to break them off. . . . According to Attorney General Francis Biddle, Roosevelt said he hoped for an "incident" in the Pacific to bring the United States into the European war.
At present, however, seventy years after these events, probably not one American in 1,000—nay, not one in 10,000—has an inkling of any of this history. So effective has been the pro-Roosevelt, pro-American, pro-World War II faction that in this country it has utterly dominated teaching and popular writing about U.S. engagement in the "Good War."
In the late nineteenth century, Japan's economy began to grow and to industrialize rapidly. Because Japan has few natural resources, many of its burgeoning industries had to rely on imported raw materials, such as coal, iron ore or steel scrap, tin, copper, bauxite, rubber, and petroleum. Without access to such imports, many of which came from the United States or from European colonies in Southeast Asia, Japan's industrial economy would have ground to a halt. By engaging in international trade, however, the Japanese had built a moderately advanced industrial economy by 1941.
At the same time, they also built a military-industrial complex to support an increasingly powerful army and navy. These armed forces allowed Japan to project its power into various places in the Pacific and East Asia, including Korea and northern China, much as the United States used its growing industrial might to equip armed forces that projected U.S. power into the Caribbean, Latin America, and even as far away as the Philippine Islands.
 Roosevelt also disliked the Germans in general and Adolf Hitler in particular, and he tended to favor the British in his personal relations and in world affairs. He did not pay much attention to foreign policy, however, until his New Deal began to peter out in 1937. Thereafter he relied heavily on foreign policy to fulfill his political ambitions, including his desire for reelection to an unprecedented third term.
When Germany began to rearm and to seek Lebensraum aggressively in the late 1930s, the Roosevelt administration cooperated closely with the British and the French in measures to oppose German expansion. After World War II commenced in 1939, this U.S. assistance grew ever greater and included such measures as the so-called destroyer deal and the deceptively named Lend-Lease program. In anticipation of U.S. entry into the war, British and U.S. military staffs secretly formulated plans for joint operations. U.S. forces sought to create a war-justifying incident by cooperating with the British navy in attacks on German U-boats in the northern Atlantic, but Hitler refused to take the bait, thus denying Roosevelt the pretext he craved for making the United States a full-fledged, declared belligerent—a belligerence that the great majority of Americans opposed.
In June 1940, Henry L. Stimson, who had been secretary of war under William Howard Taft and secretary of state under Herbert Hoover, became secretary of war again. Stimson was a lion of the Anglophile, northeastern upper crust and no friend of the Japanese. In support of the so-called Open Door Policy for China, Stimson favored the use of economic sanctions to obstruct Japan's advance in Asia. Treasury Secretary Henry Morgenthau and Interior Secretary Harold Ickes vigorously endorsed this policy. Roosevelt hoped that such sanctions would goad the Japanese into making a rash mistake by launching a war against the United States, which would bring in Germany because Japan and Germany were allied.
The Roosevelt administration, while curtly dismissing Japanese diplomatic overtures to harmonize relations, accordingly imposed a series of increasingly stringent economic sanctions on Japan. In 1939, the United States terminated the 1911 commercial treaty with Japan. "On July 2, 1940, Roosevelt signed the Export Control Act, authorizing the President to license or prohibit the export of essential defense materials." Under this authority, "[o]n July 31, exports of aviation motor fuels and lubricants and No. 1 heavy melting iron and steel scrap were restricted." Next, in a move aimed at Japan, Roosevelt slapped an embargo, effective October 16, "on all exports of scrap iron and steel to destinations other than Britain and the nations of the Western Hemisphere." Finally, on July 26, 1941, Roosevelt "froze Japanese assets in the United States, thus bringing commercial relations between the nations to an effective end. One week later Roosevelt embargoed the export of such grades of oil as still were in commercial flow to Japan."  The British and the Dutch followed suit, embargoing exports to Japan from their colonies in Southeast Asia.
Roosevelt and his subordinates knew they were putting Japan in an untenable position and that the Japanese government might well try to escape the stranglehold by going to war. Having broken the Japanese diplomatic code, the American leaders knew, among many other things, what Foreign Minister Teijiro Toyoda had communicated to Ambassador Kichisaburo Nomura on July 31: "Commercial and economic relations between Japan and third countries, led by England and the United States, are gradually becoming so horribly strained that we cannot endure it much longer. Consequently, our Empire, to save its very life, must take measures to secure the raw materials of the South Seas."
 Yet they withheld this critical information from the commanders in Hawaii, who might have headed off the attack or prepared themselves to defend against it. That Roosevelt and his chieftains did not ring the tocsin makes perfect sense: after all, the impending attack constituted precisely what they had been seeking for a long time. As Stimson confided to his diary after a meeting of the War Cabinet on November 25, "The question was how we should maneuver them [the Japanese] into firing the first shot without allowing too much danger to ourselves." After the attack, Stimson confessed that "my first feeling was of relief . . . that a crisis had come in a way which would unite all our people."