July 25, 1940: The US prohibited the export of oil to countries outside the Americas and Great Britain. This decision was confirmed on August 1, 1941 when it is modified to include aviation fuel and allow exports to all countries of the British Empire as well.
September 16, 1940: The Selective Service Bill became law. All males between the ages 21-35 were now subject to compulsory induction into the armed forces.
September 26, 1940: An embargo on scrap iron and steel exports to Japan was initiated.
March 30, 1941: US took German, Italian and Dutch ships into “protective custody.”
April 4, 1941: British warships were given permission to be repaired and refueled in the US.
April 14, 1941: Secret talks were held in New York between US and Icelandic representatives concerning the replacement of British troops by Americans. On July 7th, US troops began to arrive in Iceland.
April 24, 1941: Roosevelt formally ordered US warships to report the movement of German warships west of Iceland.
June 14, 1941: German and Italian assets in the US were frozen.
June 16, 1941: German and Italian consulates as well as offices of other German agencies in the US were ordered to close.
July 26, 1941: The US (and Britain) froze Japanese assets. The Dutch East Indies followed-up two days later and cancelled its oil contracts as well. These moves resulted in the loss to Japan of 75% of its foreign trade and 90% of its oil supplies.
September 1, 1941: The US Navy was allowed to escort convoys in the Atlantic comprising ships of any nation provided an American merchant ship was present.
September 4, 1941: The USS Greer was accidentally attacked by a German U-Boat.
September 11, 1941: Roosevelt ordered US warships to “shoot on sight” at German warships in waters “the protection of which is necessary for American defense.”
September 15, 1941: The Attorney General ruled that the Neutrality Act did not prevent US ships from carrying war material to British possessions in the Near and Far East or in the Western Hemisphere.
October 9, 1941: Roosevelt asked Congress to allow the arming of US merchant ships and to repeal sections of the Neutrality Act.
October 16-17, 1941: The US destroyer Kearny sustained casualties (including 11 dead) during a convoy battle in the Atlantic with U-Boats.
October 31, 1941: The US destroyer Reuben James was sunk by a U-Boat with the loss of 100 of its crew.
November 13, 1941: Congress altered the Neutrality Act to allow US merchant ships to be armed and to enter war zones.