AP

John Locke

English philosopher whose ideas on natural rights—life, liberty, and property—and the social contract heavily influenced Enlightenment thought and democratic revolutions.

Voltaire

French Enlightenment thinker who advocated for freedom of religion, freedom of speech, and separation of church and state, sharply criticizing absolute monarchy and religious intolerance.

Estate System

The rigid social hierarchy of pre-revolutionary France dividing society into the clergy, the nobility, and the commoners who bore the primary tax burden.

Treaty of Brest-Litovsk

The March 1918 peace agreement signed between the newly established Bolshevik government and the Central Powers, officially ending Russia's involvement in World War I.

Unrestricted Submarine Warfare

The German naval policy of sinking merchant and civilian ships without warning, a primary factor driving the United States to declare war in 1917.

Zimmermann Telegram

A secret 1917 German diplomatic proposal encouraging Mexico to declare war on the United States, intercepted by the British and widely publicizing the push for American intervention.

Central Powers

The World War I wartime alliance consisting of Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria.