World War I: Photos of the 'Great War' that shaped the twentieth century

On April 6, 1917, the United States formally entered the conflict in Europe, declaring war against Germany to join on the side of Allied nations.

When the war first began in 1914, President Woodrow Wilson strove to maintain American neutrality, but over two million U.S. troops would eventually go on to serve in a war that permanently transformed the world and significantly shaped the course of the twentieth century, both at home and abroad.

The assassination of Archduke Francis Ferdinand of Austria and his wife Sofia in Sarajevo on June 28, 1914, set off a chain of events that culminated in a world war.

The assassinations spurred Britain, France, Italy, and Russia to create an elaborate network of treaties to align against the Central Powers — which included Germany, the Austro-Hungarian Empire, the Ottoman Empire.

“The United States must be neutral in fact as well as in name during these days that are to try men’s souls. We must be impartial in thought as well as in action, must put a curb upon our sentiments as well as upon every transaction that might be construed as a preference of one party to the struggle before another,” Wilson said, according to the Library of Congress.

On April 2, President Wilson asked Congress to declare war against Germany, specifically citing Germany’s renewed submarine policy as “a war against mankind.”

“The world must be made safe for democracy,” Wilson warned.

On April 4, the Senate voted to declare war against Germany by a vote of 82-6. On April 6, the House of Representatives passed the resolution in a vote of 373 to 50, according to the National World War I Museum and Memorial.

Although published photographs and captions were censored during the war, photographs recorded some social aspects of the time, according to Professor of Conflict Studies at Wolverhampton University, Stephen Badsey. World War I was also the first major conflict to occur after the camera became more accessible.

Take a look at photos of what happened before, during and after the U.S. joined the “Great War” of 1914-1918.

Germany had formally surrendered on Nov. 11, 1918, which halted fighting but not the war.

The war formally ended on June 28, 1919, when Germany and the Allied Nations signed the Treaty of Versailles, which also provided for the creation of the League of Nations.

Camille Fine is a trending visual producer on USA TODAY's NOW team.

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This article originally appeared on USA TODAY: World War I: Photos of the calamity that shaped the twentieth century