Lesson #22: From Neutrality to War

The British ship Lusitania is sunk by a German U-boat

Germany reinstates unrestricted submarine warfare

The U.K. intercepts the Zimmerman note

A revolution in Russia unseats Czar Nicholas II

The U.S. House of Representatives votes to declare war on Germany

the World War I coalition, headed by Germany and Austria-Hungary and later including the Ottoman Empire and Bulgaria, that opposed the Allied powers

a German submarine that was the first submarine employed in warfare, initially used during World War I

an unarmed British ocean liner whose sinking by a German U-boat on May 7, 1915, influenced the U.S. decision to enter World War I

the World War I coalition, headed by France, Britain, and Russia and later including Portugal, Japan, and Italy, that opposed the Central powers

during World War I, a German military policy of staging submarine attacks on Allied and neutral nations' unarmed ocean liners without advance warning

during World War I, a German promise in 1916 to begin giving advance warning of submarine attacks on ocean liners and to spare the lives of passengers and crew

beginning in 1915, before U.S. entry into World War I, a movement led by former president Theodore Roosevelt that called on the government to increase U.S. military strength and convince Americans of the need for U.S. involvement in the war

during World War I, a coded telegram that German foreign minister Arthur Zimmermann sent to the German minister in Mexico proposing that if the United States entered the war, Mexico and Germany should become allies; it helped influence the United States to declare war on Germany five weeks later