The Angel of Mons

In 1914, war broke out in Europe and soon spread around the globe. It seemed that everyone knew this war was inevitable and had been preparing for it for years but were still surprised when it happened. Germany was going to fight a two or three front war so it decided to violate International law and attack France by way of Belgium, thus bypassing all the defenses the French had built on their border with Germany. By doing this, Germany hoped to knock France out of the war before England could tap into its empire to bring men to France's aid.
When the war broke out, tens of thousands of British men enlisted, but it would be about two months before they were trained and transported to France. A small British force was sent over right away, but it was minute compared to the German army.
Seeing this huge disadvantage, the British sent some 3,000 untrained Irish volunteers straight into combat, with no training at all.
Some of the Irish volunteers were assigned to the 4th Dubliners and assigned to hold a vital bridge across a canal near Mons.
The Imperial German Army was sweeping towards Mons with over 200,000 men and the British and French could barely field 30,000 to stop them.
To everyone's surprise, the Allies stopped the German offensive cold but Allied Command felt the position near Mons couldn't be held so they ordered a retreat back towards Paris. The untrained Irish were among two or three units that were ordered to stay behind and hold at all costs, to allow the other 27,000 men to retreat safely.
Once more, the untrained, outgunned Allies stood up to overwhelming odds and denied the German advance.
Newspapers worldwide covered the heroic stand and Mons was seen as a huge victory for the British and their allies.
Then things got weird.

A little backstory is needed first.
The 1890s saw a revival of spiritualism and the occult in England and Europe. Photography was fairly new and people didn't realize how easy it was to fake photos so when pictures that seemed to capture fairies and the like were published, it caused any people to believe they were real.
One of the best-selling authors of the day went by the pen name of Arthur Machen, and it could be said he was the Stephan King of the day.
By the time 1914 rolled around, Machen's income from his writings had dwindled and he took a job as a war correspondent, while still writing short fictional stories for several newspapers.
So it is now the early fall of 1914 and British newspapers can't get enough of the heroic stand at Mons. Arthur Machen covers the battle extensively in numerous news articles. One weekly newspaper features his reporting on the front page, while also publishing two short stories of his in the same edition. One of the short stories tells of a unit in Mons that is about to be overrun when a mysterious troop comes to their aid. Wearing ancient armor and armed only with long bows, the new troop drives back the Germans and saves the British line. When the Irish greet their saviors, it is revealed that they are the English dead from the Battle of Agincourt, returned to save England once more. With the Germans stopped, the ghost army literally fades away before the men's eyes.

Machens fictional short story gets reprinted in dozens of publications, mostly religious in nature, and before long, it is widely accepted that the men at Mons were saved by a higher power. Dozens of witnesses, including some high-ranking officers, swear they witnessed it and all sorts of strange reports come in. A French aviator claims that Joan of Arc pulled him from his burning plane. A British officer swears St Michael riding a white horse rescued his battalion. Tales of shimmering angels guiding lost troops back to safety are commonplace and German prisoners comment that they couldn't believe that men armed with bows were able to stop them. Supposedly, the German High Command thought the British had used poison gas as many Germans were found dead, yet not wounded.
By 1915, these reports were so common that Parliament ordered an investigation into them. The more Machen claimed his story was fiction, the less he was believed, and by 1916 not accepting the stories as true was seen as unpatriotic.
As the war settled down into the slaughter of trench warfare, these stories faded away but the 1920s saw a new interest in them as more and more men claimed to be eyewitnesses. Arthur Machen saw a huge increase in the sale of his stories and books, all the while insisting his story was fiction.
Today, there are numerous statues honoring the Angels of Mons throughout England, Ireland, and on the battlefield itself.
How a fictional short story inspired such a reaction is still a matter of debate. Were these professional soldiers all liars, were they victims of mass hypnosis or was there something to it?
In Portugal, three years later, 70,000 people claimed to have watched the sun dance.