Cause: German unrestricted submarine warfare. Effect: Increased anti-German sentiment in the US and moved the US closer to entering WWI.

Cause: Germany sought an alliance with Mexico against the US. Effect: Further fueled anti-German sentiment and pushed the US to declare war on Germany.

Cause: Allied desire to punish Germany and establish lasting peace. Effect: Imposed harsh terms on Germany, leading to resentment and instability, and the US Senate rejected the treaty.

Cause: Concerns about the League of Nations and entanglement in foreign affairs. Effect: The US pursued a policy of isolationism in the 1920s.

Cause: Belief in the necessity of military strength. Effect: Arms race and increased tensions among European powers.

Cause: Desire for security and mutual support. Effect: A small conflict could escalate into a larger war.

Cause: Intense pride and devotion to one's nation. Effect: Increased tensions and conflicts among nations.

Cause: Competition for colonies and resources. Effect: Increased tensions and conflicts among European powers.

Cause: Serbian nationalist assassinated the Archduke. Effect: Triggered a chain reaction of alliances and declarations of war, leading to WWI.

Cause: Wilson aimed for a just and lasting peace. Effect: Influenced the peace process but was largely rejected by other Allied leaders.

The assassination of Archduke Franz Ferdinand in 1914 sparked World War I by triggering a chain reaction of alliances and declarations of war.

The sinking of the Lusitania in 1915, a British passenger liner, by a German U-boat, killing 128 Americans, increased anti-German sentiment in the US.

A secret diplomatic communication issued from the German Foreign Office in January 1917 that proposed a military alliance between Germany and Mexico if the United States entered World War I against Germany.

Expanded the size of the army and the National Guard.

Authorized the federal government to raise a national army for the American entry into World War I through conscription.

A major part of the final Allied offensive of World War I that stretched along the entire Western Front.

The Treaty of Versailles was the peace treaty that ended World War I, imposing harsh terms on Germany.

The US Senate refused to ratify the Treaty of Versailles due to concerns about the League of Nations and entanglement in foreign affairs.

A battle fought during the German Spring Offensive in World War I, near the Marne River in France.

The Battle of Chateau-Thierry took place in July 1918 and was one of the first actions the American Expeditionary Forces (AEF) fought in World War I.

The aggressive build-up of a nation's military forces.

Agreements between countries to support each other in case of conflict.

Intense pride and devotion to one's nation, often leading to a belief in its superiority.

The policy of extending a nation's power and influence through colonization and control of other territories.

A type of combat in which opposing sides fight from trenches facing each other, resulting in a stalemate and high casualties.

A naval warfare tactic where submarines sink vessels without warning, violating international law.

The right of a people to choose their own form of government without external influence.

Payments made by a defeated nation to compensate for war damages.

A policy of remaining apart from the affairs or interests of other groups, especially the political affairs of foreign countries.

An international organization established after World War I to promote peace and cooperation among nations.