<P> President Roosevelt tried to avoid repeating what he saw as Woodrow Wilson's mistakes in World War I. He often made exactly the opposite decision . Wilson called for neutrality in thought and deed, while Roosevelt made it clear his administration strongly favored Britain and China . Unlike the loans in World War I, the United States made large - scale grants of military and economic aid to the Allies through Lend - Lease, with little expectation of repayment . Wilson did not greatly expand war production before the declaration of war; Roosevelt did . Wilson waited for the declaration to begin a draft; Roosevelt started one in 1940 . Wilson never made the United States an official ally but Roosevelt did . Wilson never met with the top Allied leaders but Roosevelt did . Wilson proclaimed independent policy, as seen in the 14 Points, while Roosevelt always had a collaborative policy with the Allies . In 1917, United States declared war on Germany; in 1941, Roosevelt waited until the enemy attacked at Pearl Harbor . Wilson refused to collaborate with the Republicans; Roosevelt named leading Republicans to head the War Department and the Navy Department . Wilson let General John J. Pershing make the major military decisions; Roosevelt made the major decisions in his war including the "Europe first" strategy . He rejected the idea of an armistice and demanded unconditional surrender . Roosevelt often mentioned his role in the Wilson administration, but added that he had profited more from Wilson's errors than from his successes . </P> <P> Political scientist Roberta Wohlstetter explores why all American intelligence agencies failed to predict the attack on Pearl Harbor . The basic reason was that the Japanese plans were a very closely held secret . The attack fleet kept radio silence and was not spotted by anyone en route to Hawaii . There were air patrols over Hawaii, but they were too few and too ineffective to scan a vast ocean . Japan Navy spread false information--using fake radio signals--to indicate the main fleet was in Japanese waters, and suggested their main threat was north toward Russia . The U.S. had MAGIC, which successfully cracked the Japanese diplomatic code . However, the Japanese Foreign Ministry and its diplomats were deliberately never told about the upcoming attack, so American intelligence was wasting its time trying to discover secrets through MAGIC American intelligence expected attacks against British and Dutch possessions, and were looking for those clues . At Pearl Harbor, they focused on predicting local sabotage . There was no overall American intelligence center--the forerunner of the Central Intelligence Agency (CIA) was formed during . In 1941 no one coordinated the masses of information coming in from the Army, Navy, and State department, and from British and Dutch allies . The system of notification was flawed, so the what the sender thought was an urgent message did not appear urgent to the recipient . After the attack, congressional investigators identify and link together all sorts of small little signals pointing to an attack, while they discarded signals pointing in other directions . Even in hindsight there was so much confusion, noise, and poor coordination that Wohlstetter concludes no accurate predictions of the attack on Pearl Harbor was at all likely before December 7 . </P> <P> The same pattern which emerged with the first world war continued with the second: warring European powers, blockades, official U.S. neutrality but this time President Roosevelt tried to avoid all of Wilson's mistakes . American policy substantially favored Britain and its allies, and the U.S. getting caught up in the war . Unlike the loans in World War I, the United States made large - scale grants of military and economic aid to the Allies through Lend - Lease . Industries greatly expanded to produce war materials . The United States officially entered World War II against Germany, Japan, and Italy in December 1941, following the Japanese surprise attack on Pearl Harbor . This time the U.S. was a full - fledged member of the Allies of World War II, not just an "associate" as in the first war . During the war, the U.S. conducted military operations on both the Atlantic and Pacific fronts . After the war and devastation of its European and Asian rivals, the United States found itself in a uniquely powerful position due to the lack of damage to its domestic industries . </P> <P> After 1945, the isolationist pattern characterizing the inter-war period had ended for good . It was Franklin Roosevelt policy to establish a new international organization that would be much more effective than the old League of Nations, and avoid its flaws . He successfully sponsored the formation of the United Nations . </P>

How did the us foreign policy change during ww2
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