Two American soldiers, Cpl. Howard Thompson and James H. White, who were part of a group that killed and captured several Germans on March 7, 1918, pose with a pistol taken from a German soldier. Photo taken in Ancerviller, France, on March 11, 1918. Image courtesy of the Library of Congress/Handout via Reuters

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Photos: When tanks replaced horses, and the birth of other WWI weapons

World Apr 6, 2017 2:57 PM EDT

It was 100 years ago today that the United States officially entered World War I, when Congress voted to declare war on Germany on April 6, 1917.

After more than two years of trying to remain neutral, the U.S. under President Woodrow Wilson joined Allied Powers Britain, France, Italy and Russia against the Central Powers of Germany, Austria-Hungary and Turkey.

From the start of the war in 1914 to its bitter end in 1918, an estimated 17 million people — civilian and military — had died. About 4.7 million Americans, who either volunteered or were drafted, served in the war and about 53,000 died in action. After devastating losses on all sides, the Allies and Germany signed an armistice on Nov. 11, 1918.

Most of the period’s technological advancements, including machine guns, explosive shells, chlorine gas and tanks that could roll over trenches, were aimed at delivering deeper blows to one’s enemy.

Sergeant Stubby, the most decorated war dog of World War I, visited the White House and President Calvin Coolidge in November 1924. Image courtesy of Wikimedia Commons

The war also introduced the world to Sergeant Stubby, a dog who served in the trenches with American troops for 18 months. The terrier, deemed the most decorated war dog of World War I, will be the subject of an animated movie planned for release in April 2018.

You can view photos of some of the war’s technological developments below.

U.S. Marines form a line in France in an undated photo taken during World War I. Image courtesy of the Library of Congress/Handout via Reuters

American soldiers keep watch in a trench in France in an undated photo taken during World War I. Image courtesy of the Library of Congress/Handout via Reuters

American troops undergo grenade gun training in France in an undated photo taken during World War I. Image courtesy of the Library of Congress/Handout via Reuters

U.S. Army soldiers playing baseball in France in 1917. Image courtesy of the Library of Congress/Handout via Reuters

U.S. soldiers of the 82nd Division stand in formation at Camp Gordon, Georgia in 1917 for service in World War I. The division would later become the 82nd Airborne Division. Image courtesy of the U.S. Army/Handout via Reuters

American, British, French and German gas masks are seen in an undated photo taken during World War I. Image courtesy of the Library of Congress/Handout via Reuters

American soldiers react to a gas attack in an undated photo, likely used for training purposes, taken during World War I. Image courtesy the Library of Congress/Handout via Reuters

An American gun crew from Regimental Headquarters Company, 23rd Infantry, fires a 37mm gun during an advance against German entrenched positions in an undated photo taken during World War I. Image courtesy of the Library of Congress/Handout via Reuters

Tanks were developed to barrel over trenches filled with soldiers. Here, a British Mark IV tank didn’t quite make it during the British-German Battle of Cambrai in France, Nov. 20, 1917. Handout/Files via Reuters

An officer receives a camera and its film to be processed in the field in an undated photo from World War I. Handout via National Defense Intelligence College from Reuters

An American World War I observation balloon is seen in an undated handout photo originally released Dec. 9, 1917. Handout via U.S. Library of Congress

A Renault truck outfitted with mobile X-ray equipment to help doctors in the field is seen in an undated World War I photo. Handout via U.S. Army from Reuters

Wounded soldiers lie in an American field hospital in Auteuil, Paris, France around 1915 during World War I. Image courtesy of the Library of Congress/Handout via Reuters

The Big Four Allied leaders of World War I, also known as the Council of Four, included British Prime Minister David Lloyd George, Italian Premier Vittorio Emanuele Orlando, French Premier Georges Clemenceau and President Woodrow Wilson. They are pictured here in Versailles at the Paris peace conference, May 27, 1919. Handout via U.S. Library of Congress from Reuters

U.S. soldiers return to Washington, D.C. in an undated photo following service in World War I. Image courtesy of the Library of Congress/Handout via Reuters

Left: Two American soldiers, Cpl. Howard Thompson and James H. White, who were part of a group that killed and captured several Germans on March 7, 1918, pose with a pistol taken from a German soldier. Photo taken in Ancerviller, France, on March 11, 1918. Image courtesy of the Library of Congress/Handout via Reuters

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Larisa Epatko Larisa Epatko

Larisa Epatko produces multimedia web features and broadcast reports with a focus on foreign affairs for the PBS NewsHour. She has reported in places such as Jordan, Pakistan, Iraq, Haiti, Sudan, Western Sahara, Guantanamo Bay, China, Vietnam, South Korea, Turkey, Germany and Ireland.