On This Day: U.S. President Woodrow Wilson vows to abandon neutrality and enter First World War

APRIL 2, 1917: U.S. President Woodrow Wilson vowed to send American troops to Europe and help the British and French fight the First World War on this day in 1917.

He asked Congress to declare war on Germany and abandon neutrality after five U.S. merchant ships were sunk when the Kaiser ordered all-out submarine warfare.

Four days later, members of the House of Representatives and Senate held a joint session and voted to enter the conflict that had been raging since August 1914.

Wilson, who had called for a “war to end all wars” that would “make the world safe for democracy”, had hitherto been a passionate advocate of neutrality.

Pacifism – and hatred of Britain - was also popular, particularly among the ten million German and six million Irish Americans who tended to vote for Wilson’s Democrats.

But public opinion – notably among the majority who still claimed either English, Scottish or Welsh ancestry – began to shift following news of German atrocities.

Americans had been outraged by the Rape of Belgium and the 1915 sinking of the British passenger ship RMS Lusitania.

And when Kaiser Wilhelm II ordered all ships heading to Britain to be attacked – knowing this would likely mean war with the U.S – they finally demanded combat.

But American troops did not see action until November 1917, as first Wilson had to raise an army in what was then the largest mobilisation in the country's history.

Having previously called for neutrality “in thought and deed”, he had maintained a peacetime-sized force of 190,000 soldiers to prevent making any military threats.

But after Congress authorised conscription in May, more than four million men were soon drafted into the American Expeditionary Force.

A British Pathé newsreel showed Wilson inspecting some the newly formed units before they left for Europe.

The mighty U.S. industrial machine, which since 1914 had already generated 20% economic growth by arming other belligerents, also went into overdrive.

The American entrance was a shot in the arm to the beleaguered British and French, who had been bogged down in a war of attrition in trenches for over three years.

It also came at a vital time as the Bolsheviks in Russia had just signed a peace treaty with Germany following the October Revolution.

In turn, the Kaiser was now able to funnel millions more troops away from the East and on to the Western Front.

But the U.S. quickly flooded Britain, which had been its colonial master until the American Revolutionary War ended 134 years earlier, with food and weapons.

It meant that now Germany and its ally Austro-Hungary were the nations at greatest risk of being starved to death by naval blockades.

The Kaiser has also seriously underestimated the Americans’ might.

They fought with distinction in thirteen campaigns, although their contribution was relatively small and they did not begin to make much of an impact until July 1918.

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However, the Allies were planning a major attack in 1919 that would involve 1.5million U.S. troops as well as millions of others.

Faced with such terrifying force and America’s potential, the Kaiser knew the war was unwinnable and signed an Armistice ending it on November 11, 1918.

The war also had a massive affect on the American home front - and the rising anti-German sentiment would lead to two quirks of history.

On a temporary basis, the names of foods such as hamburgers and sauerkraut were changed to the more American monikers of liberty sandwiches and liberty cabbage.

But it also enabled the prohibition of alcohol after the German-dominated brewers had become hate figures and could no longer stop the rising temperance movement.

The 18th Amendment, which was passed in December 1917, was not repealed until 1933 after the booze ban ushered in a crime wave that was impossible to police.