World War I was a global war fought from 1914 to 1918 in which allies including Great Britain, France, Russia, and the United States defeated Germany, Austria-Hungary, Turkey, and Bulgaria. The Zimmerman Telegram was a 1917 proposal from Germany to Mexico to join the Central Powers if the US entered WWI against them, which was intercepted and helped generate American support for entering the war. The Selective Service Act authorized the US government to raise a national army through conscription, while the American Expeditionary Force fought alongside allies in Europe against Germany from 1917-1918 under General John J. Pershing.

1. World War I
A war fought from 1914 to 1918, in which Great
Britain, France, Russia, Belgium, Italy, Japan,
the United States, and other allies defeated
Germany, Austria-Hungary, Turkey, and
Bulgaria.

2. Zimmerman Telegram
A 1917 diplomatic proposal from the German
Empire for Mexico to join the Central Powers,
in the event of the United States entering
World War I on the side of the Entente Powers.
The proposal was intercepted and decoded by
British intelligence. Revelation of the contents
outraged American public opinion and helped
generate support for the United States
declaration of war on Germany in April of that
year.

3. Freedom of the Seas
A principle in the international law and law of the sea. It
stresses freedom to navigate the oceans. It also
disapproves of war fought in water. The freedom is to be
breached only in a necessary international agreement.

4. Lusitania
A British ocean liner, holder of the Blue Riband and briefly
the world's biggest ship. She was launched by
the Cunard Line in 1907, at a time of fierce competition
for the North Atlantic trade. In 1915 she was torpedoed
and sunk by a German U-boat, causing the deaths of
1,198 passengers.

5. Sussex Pledge
A promise made in 1916 during World War I by Germany to
the United States prior to the latter's entry into the
war.
• Passenger ships would not be targeted;
• Merchant ships would not be sunk until the presence of
weapons had been established, if necessary by a search
of the ship;
• Merchant ships would not be sunk without provision for
the safety of passengers and crew.

6. Submarine Warfare
Submarine warfare in World War I was partly a
fight between German U-Boats and Atlantic
supply convoys bound for Great Britain. British
and Allied submarines conducted widespread
operations in the Baltic, North Sea, Atlantic,
Mediterranean and Black Seas. A type of naval
warfare in which submarines sink vessels such
as freighters and tankers without warning, as
opposed to attacks per prize rules (also known
as "cruiser rules").

7. Selective Service Act
The Selective Service Act or Selective Draft Act
authorized the federal government to raise a
national army for the American entry into
World War I through conscription.

8. Schenck v. U.S.
Defendant's criticism of the draft was not
protected by the First Amendment, because it
created a clear and present danger to the
enlistment and recruiting service of the U.S.
armed forces during a state of war.

9. American Expeditionary Force
The American Expeditionary Forces were the
United States Armed Forces sent to Europe in
World War I. During the United States
campaigns in World War I the AEF fought in
France alongside French and British allied
forces in the last year of the war, against
Imperial German forces

10. John J. Pershing
A general officer in the United States Army who
led the American Expeditionary
Forces in World War I. Pershing is the only
person to be promoted in his own lifetime to
the highest rank ever held in the United States
Army—General of the Armies.

11. Battle of Argonne Forest
Part of the final Allied offensive of World War I
that stretched along the entire western front.
It was fought from September 26, 1918, until
the Armistice.

12. Alvin York
One of the most decorated American soldiers
in World War I. He received the Medal of
Honor for leading an attack on
a German machine gun nest, taking 32
machine guns, killing 28 German soldiers and
capturing 132 others.

13. Trench Warfare
A type of combat in which opposing troops fight
from trenches facing each other.

14. U-Boats
A German submarine used in World War I

15. President Woodrow Wilson
As World War I erupts in Europe,
President Woodrow Wilson formally proclaims
the neutrality of the United States, a position
that a vast majority of Americans favored, on
August 4, 1914.

16. Fourteen Points
The "Fourteen Points" was a 1918 statement by
United States President Woodrow Wilson that
the Great War was being fought for a moral
cause and for postwar peace in Europe.

17. Versailles Treaty
The Treaty of Versailles was one of the peace
treaties at the end of World War I. It ended
the state of war between Germany and the
Allied Powers. It was signed on 28 June 1919,
exactly five years after the assassination of
Archduke Franz Ferdinand.

18. Reparations
World War I reparations were the payments and
transfers of property and equipment that
Germany was forced to make under the Treaty
of Versailles following its defeat during World
War I.

19. League of Nations
International organization created to ensure
world stability.

20. Henry Cabot Lodge
An American Republican Senator and historian
from Massachusetts. He is best known for his
positions on foreign policy, including his
opposition to U.S. involvement in WWI, and his
battle with President Woodrow Wilson in 1919
over the Treaty of Versailles. Lodge demanded
Congressional control of declarations of war;
Wilson refused and the United States Senate
never ratified the Treaty nor joined the
League of Nations.

21. Isolationism
A policy of national isolation by abstention from
alliances and other international political and
economic relations.