One hundred years ago, on April 6, 1917, the U.S. House of Representatives approved President Woodrow Wilson’s declaration of war articles by a vote of 373 to 50. 

Two days earlier the U.S. Senate had voted 82 to 6 to declare war against Germany.  When the President signed declaration bill, America formally entered World War I.

When World War I broke out in July and August of 1914, President Wilson pledged to keep the United States neutral. 

This was a popular decision among the vast majority of Americans. Maintaining a neutral posture proved difficult since Wilson was pro-British, and that nation was America’s closest trading partners and political ally. 

To that end, tension soon arose between the United States and Germany over the latter’s attempted quarantine of the British Isles through the use of mines and U-boats or submarines. 

Several U.S. ships traveling to Britain were damaged or sunk by German mines, and in February 1915, Germany announced unrestricted warfare against all ships, neutral or otherwise, that entered the war zone around Britain. 

One month later, Germany announced that a German cruiser had sunk the William P. Frye, a private American vessel. 

Wilson was outraged, but the German government apologized and called the attack an unfortunate mistake. On May 7, 1915, the British-owned Lusitania ocean liner was torpedoed without warning just off the coast of Ireland. 

Of the 1,959 passengers, 1,198 were killed, including 128 Americans. 

The German government maintained that the Lusitania was carrying munitions, but the U.S. demanded reparations and an end to German attacks on unarmed passenger and merchant ships.

In August, Germany pledged to see to the safety of passengers before sinking unarmed vessels, but in November sunk an Italian liner without warning, killing 272 people, including 27 Americans.

With those attacks, public opinion in the United States began to turn irrevocably against Germany.

Even though, the President won re-election in November 1916 declaring he kept America out of war, the advent of war soon became imminent. 

Late in 1916, Wilson’s efforts to mediate a peaceful and “non-victorious” end to the war failed. 

Worse still, in January 1917, British operatives intercepted a cable from the German foreign minister, Baron von Zimmerman to the Mexican President Venustiano Carranza, offering to help return all lands Mexico had lost in 1848 to America if the Mexicans would attack the U.S. 

When the British presented the telegram to Wilson he was outraged and sought a reason to declare war. 

That reason soon came in February 1917, when Germany, determined to win its war of attrition against the Allies, announced the resumption of unrestricted warfare in war-zone waters.

Three days later, the United States broke diplomatic relations with Germany, and just hours after that the American liner Housatonic was sunk by a German U-boat. 

On Feb. 22, Congress passed a $250 million arms appropriations bill intended to make the United States ready for war. 

In late March, Germany sunk four more U.S. merchant ships, and on April 2, President Wilson appeared before Congress and called for a declaration of war against Germany.

It was one thing to declare war and, yet another to send troops to fight. 

Indeed, it was not until June 26, the first 14,000 U.S. infantry troops known as the Rainbow Division, commanded by Gen. John J. Pershing, landed in France to begin training for combat. 

Still, it was not until a year later, that the American’s had enough troops to begin to take offensive action. Pershing refused to blend U.S. forces into British and French units.

In the summer of 1918, American units defeated German troops at Chateau Thierry and Belleau Woods to help stop the infamous Ludendorff Offensive Germany’s last great offensive. 

During the Saint-Mihiel offensive, Gen. Billy Mitchell, between September 12 and 16, led 1,481 U.S. Army Air Service aircraft against German targets all along the battle front and in the rear areas as far as Germany itself. 

Thus, after four years of bloody stalemate along the western front, the entrance of America’s well-supplied forces into the conflict marked a major turning point in the war and helped the Allies to victory.  American ground forces and airpower spearheaded the great Allied offensives of the fall of 1918 that led to the signing of an armistice and cease fire on Nov. 11, 1918 on the eleventh hour of the eleventh day of the eleventh month. 

More than two million American soldiers had served on the battlefields of Western Europe.  The total number of military and civilian casualties in World War I was more than 40 million. 

Of those, 20 million were killed in action, nearly half dying of disease and wounds. Another 30 million were wounded, many severely. 

In 1919, in the aftermath of war, an influenza epidemic broke out, mostly among the surviving wounded civilians and combatants. 

Ultimately, this led to more than 11 million military and about nine million civilian deaths. 

While American casualties were significant, the official total of 116,516 dead and 323,000 wounded pales by comparison to the 200,000 killed in World War II and 600,000 lost in the Civil War. 

It is worth noting that of those who died, 53,402 were killed in action and 63,114 died from wounds or disease, mostly influenza. World War I still ranks as one of the bloodiest conflicts in  human history.