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.

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.