How did US enter in to WW1 and WW2 and compare the aftermaths of the war in terms of US’s foreign policy

What were reasons the United States entered World War I?

1. Unrestricted submarine warfare:

  • sinking of the ship Lusitania (1915) in which many passengers died
  • The “Sussex” pledge (1916)-a promise made by Germany to not harm US’s ships but it was broken in 1917
  • Germany renews unrestricted U Boat attacks (1917)

2. American Propaganda

  • Stressed German barbarism.
  • Posters depicting the Kaiser as some sort of madman.
  • Urged American to support allies throughout neutrality.
Passive agressive message from US to its citizens

3. German Dictatorship – “Make the World safe for Democracy.” – Cultural ties

4. Business Interests – US trade w/ the allies increased from 825 million in 1914 to 3.2 billion in 1916. Britain owed $2b to US, cannot let it get defeated

5. Zimmerman telegram – Germany asked Mexico to enter the war against the US on promise of return of California. US intercepted it.

What happened in US after WW1?

  1. The Treaty received enormous opposition in US as it called upon the US to support League actions.
  2. The United States did not ratify the Treaty of Versailles and did not join the League of Nations. Wilson considered this a great failure and it plagued him until his death.
  3. Turned Isolationist – wanted no further war or outside contacts. Many Americans saw US involvement in WWI as a waste of time.
  4. The result of this disillusionment was a fundamental shift in American policy from internationalism to relative isolationism.
  5. Victory had brought an emotional let-down – “the slump of idealism.” The war to make the world safe for democracy [also known as the war to end all wars] had not made the world safe for democracy, nor had it ended wars. Some twenty conflicts of varying dimensions were being waged in various parts of the world. About all that America had seemingly derived (gotten) from the war was debt, inflation, prohibition, influenza, and ingratitude from Allies whom she had strained herself to help

Causes for entering WW2:

It was a great turnaround for US to shift its policy from a isolationist policy to participate in World’s most devastating policy. How why did US change its policy?


  1. Germany Sank U.S. Merchant Ships:  The fact that the U.S. sent military aid to the United Kingdom was viewed by Germany as a hostile act. The war time supply created many jobs in US, it cannot afford to stop manufacturing them
  2. Japan’s Invasions on China:  By 1941, Japan occupied much of north and coastal China and committed atrocities there. Also US’s influence in Asia-Pacific was threatened.
  3. US public opinion: They were moved by the plight of Jews and other common people under the fascist regimes of Italy and Germany. US government and celebrities like Charlie Chaplain through films educated the public about the atrocities of these regimes.
  4. Atomic bomb: Germany was developing the atomic bomb. US realized that war needs to be won before Hitler gets the bomb.
  5. France and British: They were considered allies(fought together in WW1). Also the United States supplied Free France, United Kingdom, the Republic of China, and later the USSR and other Allied nations with food, oil, and materiel(weapons, ships, planes) between 1941 and August 1945 under the “Land-Lease” policy(mostly free). In order to recover these loans US wanted these countries to win the war. This policy ended the US’s pretense of being ‘neutral’ during the war.
  6. Japanese Attack on Pearl Harbor:  On Dec. 7, 1941, the Japanese launched a surprise attack on the U.S. navy base in Hawaii as a pre-emptive strike. The U.S. went to war with Japan on Dec. 8, 1941. On Dec. 11, Germany and Italy declared war on the United States.

After the war:

  • Like after the WW1, US after WW2 had adopted diametrically opposite foreign policy
  • The war had produced a clear winner and now there are only two super powers in the world: US and USSR. It can no longer afford to follow an isolationist policy
  • The threat of USSR’s communist propaganda meant that US had to actively seek allies and support capitalist countries
  • USA declared it self the leader of the “free world” and actively participated in cold war.
  • The present US still follows this policy of active intervention in other countries to safe-guard its “interests”


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