APUSH Unit 7: Foreign Policy in the Interwar Period

General Timeline
General Maps

Map # 1: Europe

APUSH Unit 7_ Foreign Policy Map #1.png

Map # 2: East Asia & Pacific

APUSH Unit 7_ Foreign Policy Map #2.png
Course Content

Interwar Period Foreign Policy:

Isolationism in the 1920s

International Treaties

  • US didn't join the League of Nations as it would give US a responsibility to help other nations

    • US wanted to remain isolationist & not be involved w/ affairs of other nations

  • However, US wanted peace w/ other nations, so US signed many peace treaties w/ other nations:

Washington Naval Treaty (1922)

  • Limited construction of warships by US, UK, Italy, France, & Japan

  • Prevented Japan from dominating East Asia

  • Meant to prevent a nation from becoming super dominant in their region

Kellogg-Briand Pact (1928)

  • An agreement between 62 nations to not use war to resolve any conflict

  • Relied on a moral agreement, did not have any method of enforcing it

  • Ultimately failed as it couldn't be enforced

Other Treaties


  • Four-Power Treaty (1921): Signed by US, UK, France, Japan, meant to prevent aggression in East Asia

  • Nine-Power Treaty (1922): Allowed for the continuation of Open Door Policy in China

  • Many of these treaties failed as they had no method of enforcement & couldn't combat aggression by Japan, Germany, or Italy

International Debts & Diplomacy

  • US wanted to stay isolationist, but it had to resolve its loan problems first

  • Europeans had many loans to the US, & US wanted to resolve these

    • Allies (France, UK) owed $11 billion to US​

    • Germany owed $32 billion as reparations to Allies

    • Dawes Plan (1924) allowed US to give loans to Germany & cut down German reparations

    • This created a circular debt structure, which was problematic

  • European economy was suffering, so US invested a lot there

    • American banks invested in businesses there as most other businesses were in decline

    • Because European industry was unstable, American banks became unstable

  • Pres. Coolidge then passed Fordney-McCumber Act (1922) to raise tariffs

    • Caused European industry to decline more as they couldn't export goods to US

  • US also had loans to Latin America

    • US invested a lot into Latin America to gain access to its rich natural resources​

    • Latin America also struggled to pay back the US, causing economic problems there

  • Overall, the US struggled to stay isolationist due to its investments overseas


Diplomatic Crisis in Great Depression

  • The Great Depression (1929) undid the int'l treaties of the 1920s as nations wanted more nationalism & isolationism to solve the economic crisis

    • This would eventually lead to war​

  • Hoover wanted to remove all US troops from Latin America

    • Agreed to accept any current gov in Latin America; removed his troops from there

  • Hoover proposed a moratorium on loan payments from Europe, but his assistants opposed it

    • This worsened the economic crisis in Europe

  • The ineffectiveness of diplomacy in Europe was problematic & allowed new regimes to take power

    • Hitler in Germany & Mussolini in Italy could consolidate power easily & US couldn't do anything about it

    • A similar situation happened with Japan:

Pro-military people took control of Japanese government. Japan then invaded Manchuria (Northeast China) in an event known as the Mukden Incident (1931). 

The League of Nations told Japan to stop, but Japan withdrew from the League.

US Sec of State Henry Stimson could not engage in any sanction or activity against Japan. The most he could do was not recognize Japanese control of Manchuria

  • The Mukden Incident (1931) showed how the US could not do anything to combat threats to combat world peace

    • Similar thing happened with Germany & Italy, causing WW2 in 1939​

FDR's Initial Diplomacy

FDR's Diplomacy to Combat Great Depression

  • In Jun 1933, FDR released a "bombshell" message to end the gold standard for currency

    • FDR took the US off the gold standard in Jul 1933​

  • FDR passed Johnson Debt Default Act (1934) to prevent American banks from giving loans to Europe until European nations pay back all existing loans

    • Boosted the US's stance of isolationism from European issues​

  • FDR signed Reciprocal Tariff Act (1934): Allowed FDR to reduce tariffs significantly if other nations also reduce tariffs by the same amount

    • Allowed international trade to increase

    • However, European goods struggled to compete w/ American goods, causing European economy to suffer

  • Overall, FDR wanted to help European economies while maintaining his stance of isolationism


Good Neighbor Policy in Latin America

  • FDR wanted to have better relations w/ Latin America by emphasizing economic cooperation rather than military intervention

    • US had lots of trade w/ Latin America & FDR wanted to increase them

  • Sec of State Cordell Hull signed an agreement to prevent nations in the Americas from interfering w/ the affairs of other nations

    • Known as the Good Neighbor Policy

    • Allowed US to economically dominate Latin American nations & get them to repay debts​


US's Relationship with USSR

  • US initially didn't recognize the USSR (Communist Russia) after Bolshevik Revolution (1917)

    • Didn't want to be allied w/ Communist nation​

  • Later, in 1930s, US engaged in relations w/ USSR

    • US believed forming an economic alliance w/ USSR would be really beneficial

    • US & USSR could work together to combat Japanese aggression

  • FDR signed a treaty w/ Russia to mutually recognize each other & support each other

  • Eventually, due to isolationist sentiment & lack of mutual help, this relationship started to fall apart


FDR's Isolationism

Causes of Isolationism

  • As other nations became isolated, US had to adhere to isolationism:

    • Geneva Disarmament Conference (1932) collapsed in 1934

      • Hitler & Mussolini withdrew from this agreement​

    • Japan withdrew from the treaties meant to reduce naval warfare

  • Because other international treaties failed, US was forced to adhere to isolationism


Nye Committee (1934-1936)

Sen. Gerald Nye (R-ND) led an investigation into why US joined WW1

Figured out that many bankers & financial institutions pressured Woodrow Wilson to join WW1

This led to widespread isolationist sentiment in US as they hated that banks pressured US to join WW1

Neutrality Acts (1936-1939)

Neutrality Act of 1936

  • Forbade US from exporting war supplies (guns, munitions, etc.) to any nation currently in war

  • Also forbade US from giving loans to any nation currently in war

Neutrality Act of 1937

  • Prevented US citizens from traveling on ships of nations currently in war

  • Created cash-and-carry system: Nations could get anything (except military supplies) from US if they pay in cash & transport it home themselves

Neutrality Act of 1939

  • Extended cash-and-carry system to military supplies as well

  • Still forbade US from giving loans to warring nations & from traveling themselves to deliver supplies to warring nations

Start of World War 2

Threats to Isolationism

  • US remained very isolationist since around 1935, but many totalitarian regimes in Europe threatened US's position

    • Mussolini (Italy) invaded Ethiopia in 1935 & withdrew from the League of Nations​

      • Signed Axis agreement w/ Hitler in 1936

    • Adolf Hitler (Germany) invaded Rhineland (1936) & Austria (1938)

    • Japan invaded Manchuria (1931)

    • Spain had a civil war between Fascists & Republicans, and Fascists won​​

    • Japan bombed USS Panay (1937) in China

  • All of the above events threatened US's isolationist position, but US still remained isolationist


German Aggression & Start of WW2 (1938-1939)

Hitler wanted to create an "anschluss" (union) of all German-speaking lands. He conquered Rhineland (1936) & Austria (1938)

Hitler wanted to invade Sudetenland, but France & Britain didn't want him to

France & Britain didn't want war w/ Hitler, so they signed the Munich Agreement (Sep 1938) w/ Hitler, allowing Hitler to invade Sudetenland but nothing else

Responding to Hitler's invasion of Poland, Britain & France declared war on Germany (Sep 1939)

Hitler went even further & invaded Poland in Sep 1939

Hitler invaded Sudetenland in Oct 1938. He broke the Munich Agreement & invaded rest of Czechoslovakia in Mar 1939

FDR's Aid to Allies

  • Responding to the start of war, FDR created the Neutrality Act of 1939

    • Extended cash-and-carry system to military supplies: Warring nations could buy war supplies from US if they could transport it themselves

  • US's ally, France, was defeated by Germany in Jun 1940 → All British & French troops retreated to Dunkirk

    • This significantly strained France & Britain

    • If Germany occupies Britain & France, they are literally a few days away from attacking US

  • Also, in Sep 1940 - May 1941, Germany bombed London, making Britain more in need of help

  • FDR decided to help Britain & France even more to prevent Germany from attacking US

    • FDR created a new fleet of warplanes​

    • Winston Churchill (British PM) asked FDR for help, FDR sent war materials, ships, planes, etc. to Britain

      • In exchange, US can build military bases on some British lands

  • Congress also passed Burke-Wadsworth Act (1940), creating a military draft in case of war

  • Within US, there was lots of disagreement over whether to join the war or not: 

Committee to Defend America by Aiding the Allies (CDAAA)​

  • Wanted to keep US out of war by providing financial & material aid to the Allies (France & Britain)

Fight for Freedom Committee

  • Wanted US to actually join the war & repeal Neutrality Acts

America First Committee

  • Wanted US to remain isolationist & not enter WW2

  • Had strong support of many Republicans

  • These 3 committees created lots of tension in US

  • Eventually, FDR won re-election (3rd term) in 1940

Lend-Lease System & Further Threats to US

  • After FDR's re-election in 1940, US was moving more toward war

    • In Mar 1941, Congress replaced cash-and-carry system w/ lend-lease system: Britain could borrow military supplies from US & pay back later

      • US did this b/c Britain was nearly bankrupt

    • Germany started threatening British ships in Atlantic as they'd travel to US to pick up military supplies → US would now escort supplies halfway across Atlantic​

  • Hitler invaded USSR in fall 1941 → USSR needed help from US → US extended lend-lease to USSR & created formal US-USSR alliance

  • German U-boats started to threaten US ships, so FDR ordered US ships to fire at German submarines
    • In fall 1941, USS Greer was shot by German U-boats → FDR ordered US ships to "shoot-on-sight" at German U-boats
    • In Oct 1941, USS Reuben James was sunk by German U-boats
  • In Aug 1941, US met w/ Britain to create the Atlantic Charter, a set of principles to maintain post-war peace & prosperity
    • This failed as US joined the war soon after​

Pearl Harbor Attack (Dec 1941) & US Joins the War

Japan also had a fascist militarist gov & signed Tripartite Pact w/ Hitler & Mussolini (Sep 1940)

Inspired by German success in Europe, Japan wanted to take over parts of East Asia

Japan invaded French Indochina in Sep 1940

Japan thus bombed Pearl Harbor (Dec 7, 1941). US declared war on Japan after that. Then Germany & Italy declared war on US

Japanese militants didn't want to compromise or negotiate w/ US

US imposed an oil embargo on Japan as US wanted to protect its ally, France, and its colony, French Indochina