Why did the US join World War One?

The road to the First World War was a long and complicated one, with many events leading up to America's eventual involvement.

While America was considered to be closely allied to Britain and France, the majority of Americans wanted to stay out of the war.

However, as events unfolded and tensions rose, it became increasingly clear that America would have to take sides. 

The assassination of Archduke Franz Ferdinand on the 28th of June, 1914, was one of the main triggers that led to war.

Franz Ferdinand was heir to the Austro-Hungarian throne, and his death at the hands of a Serbian nationalist group set off a series of events that would eventually lead to open war between Austria-Hungary and Serbia's allies. 

Austria-Hungary's response to the assassination was to declare war on Serbia, and this action quickly drew in Russia, who came to Serbia's defense.

From there, things escalated rapidly: Russia began mobilising its troops, Germany declared war on Russia (and later France), and Great Britain declared war on Germany.

By the 4th of August, 1914, all of the major European powers had committed to the conflict.

However, America viewed this as a European war, and did not see an immediate need to get involved. It remained officially neutral, though many Americans were beginning to sympathise with the Allied cause. 

While America did not participate in the fighting during the first few years of the war, it did provide some support to the Allies in the form of supplies and financial aid.

The industrial might of the United States was a major factor in keeping the Allies afloat during the first few years of World War One. 

One of the events that pushed America closer to joining the war was Germany's decision to begin unrestricted submarine warfare in early 1915.

This meant that German submarines would sink any ship, Allied or neutral, without warning, in an attempt to starve Britain into submission. 

The sinking of the British ocean liner Lusitania near Ireland by a German U-boat in May 1915 was a major turning point in American public opinion.

The cruise ship was carrying 1,959 passengers when it was sunk without warning. 1,195 people died, including the loss of 128 American lives.

This event angered many Americans and led to a rise in anti-German sentiment.

Despite this growing anger, President Woodrow Wilson continued to keep America neutral.

In his famous "Peace without Victory" speech, he urged Americans to remain calm and avoid being drawn into the conflict.

However, in response to the Lusitania sinking, Congress did pass the Naval Appropriations Act of 1916, which began a massive expansion of the US Navy.

This act marked the beginning of the Preparedness Movement, which called for the US to increase its military readiness in case of war. 

Also in 1915, the Preparedness Movement gained a powerful ally in the form of Theodore Roosevelt.

Roosevelt, a former President and military hero, was a strong advocate for American involvement in the war.

He suggested forming volunteer cavalry regiments, and began giving speeches across the country calling for a general sense of readiness should America need to join the conflict.

The American public held different opinions about what the US should do in regard to the First World War.

Some, like President Woodrow Wilson, called for neutrality and a focus on domestic affairs.

Others, like Theodore Roosevelt, believed that the US should take a more active role in international affairs and support the Allied side. 

The Interventionists were a group of Americans who actively called for the US to enter the war on the side of the Allies.

The group's activities included organising propaganda campaigns and holding pro-war rallies.

By 1916, it was clear that America would eventually be pulled into the war. The question was no longer if America would join, but when.

This issue played a major role in the presidential election of 1916.

Incumbent President Woodrow Wilson ran on a platform of neutrality, while his challenger, Charles Evans Hughes, argued that America should begin preparing for war.

Although Wilson won the election, it was a close race. The close result showed that the American public was divided on the issue of war, and that intervention would not be popular with everyone.

Nevertheless, Wilson continued to push for neutrality even as events began to pull America closer and closer to war. 

However, by 1917, it was clear that America would eventually be drawn into the war.

In January of that year, Germany announced that it would once more use unrestricted submarine warfare, meaning that any ship entering waters controlled by Germany could be sunk without warning.

This policy led to the sinking of several American ships, including the Aztec in April 1917. 

In early 1917, Germany made one final attempt to keep America out of the war. They did this by sending a message known as the 'Zimmerman Telegram'.

The coded telegram was sent from the German Foreign Minister, Arthur Zimmermann, to the German ambassador in Mexico.

In it, Zimmermann offered Mexican assistance in attacking America if they joined the war on Germany's side. 

The Zimmerman Telegram was intercepted by the British, who then passed it on to the American government.

When news of the telegram leaked to the public, it caused a furor. Americans were outraged that Germany would even consider supporting an attack on them, and a call for intervention in the war reached an all-time high. 

In April 1917, Congress voted to declare war on Germany and, as a result, America finally entered the First World War.

Over the next few months, America began to mobilize its forces and send them overseas.

The country also began to produce large quantities of munitions and supplies to support the Allied war effort.

From June 1917, American troops began arriving in France, where they would play a major role in 1918, turning the tide of the war in favor of the Allies. 

The events of 1914-1917 led inexorably to America's involvement in the First World War.

The assassination of Franz Ferdinand, Austria-Hungary's declaration of war on Serbia, Germany's unrestricted submarine warfare, and the sinking of American ships all played a part in convincing America to join the Allies against Germany.

In April 1917, Congress declared war on Germany, marking America's official entry into the First World War.