Warsaw -- September 1939. Polish cavalrymen saddle up, level their lances and sabres, and charge headlong into the advancing Nazi German tanks.

That has become a stock image: hapless, quixotic Poles facing the all-powerful invaders at the outbreak of World War II.

The problem is that it's a myth, experts say. Worse still, repeating it means keeping Nazi propaganda alive.

Like many legends, it was spun from a real event, explained historian Christoph Mick of Britain's University of Warwick.

On September 1, 1939, the day the Nazi offensive began, around 250 Polish cavalrymen charged a German infantry unit at Krojanty, a northern hamlet.

After dispersing the enemy, they were surprised by German armour which emerged from the woods and strafed them, killing several dozen riders and their horses.

"When German and Italian journalists arrived on the battlefield they were shown the dead horses and cavalrymen and two German tanks," said Mick.

"The story was made up by Nazi propaganda to show the backwardness of the Polish army and how much the Poles had underestimated the strength of the German Wehrmacht. Polish cavalry never attacked German tanks," he added.

Fascist Italy was already a Nazi ally, but remained neutral in the war until 1940, lending its correspondents' coverage an international credence that Nazi reports lacked.

The myth also served other Nazi purposes.

Germany's doctrine of "Blitzkrieg" -- lightning war -- was based on thrusts by its motorised Wehrmacht land forces and hammer blows from the air by the Luftwaffe.

But it was also psychological.

"Their propaganda films showed off all their tanks and planes. They put a very strong focus on that," said Polish expert Wojtek Lietz, who rides in the 8th Uhlan Regiment, a re-enactment group.

The Nazis had the edge because Germany -- forced by the victors to slash its military after losing World War I -- re-armed fast once Adolf Hitler came to power in 1933.

Other nations failed to wake up until he had stolen a march on them. Poland aimed to mechanise much of its military by 1942.

The wartime role of horses, however, was far from mythical.

In 1939, Poland still had around 320,000 cavalry, but their horses primarily were a means of getting soldiers into battle.

"The reality was that Polish cavalry were trained and used as mounted infantry. The cavalry was not supposed to fight on horseback, but dismount before joining the fight," said Jan Szkudlinski of Poland's World War II Museum.

When circumstances required, they reverted to traditional tactics, charging German troops on at least 16 occasions.

Despite their high-technology image, the Nazis had around 200,000 cavalry. Polish and German horsemen clashed at Krasnobrod in eastern Poland on September 23, two weeks before the Poles capitulated.

"If you compare the east and west, the east lacked good roads," noted Lietz. Horses were suited to the flat terrain -- proven by the cavalry battles of the 1919-1921 Polish-Bolshevik war -- and both the Wehrmacht and Red Army made extensive use of them after Germany invaded the Soviet Union in 1941.

Horsemen also fought on other fronts.

The first Germans across the River Seine during the conquest of France in 1940 were cavalrymen, and US and British cavalry battled the Japanese in the Philippines and Burma.

The Polish myth was bolstered after the war, when the country spent 45 years under communist rule.

"Their propaganda aimed to underline all the bad things about the previous government. That helped make the story stick," said Lietz.

For London-based historian Adam Zamoyski, there is an extra explanation: "People love simple stories, particularly ones that make other nations appear quaint and a little inferior."

"In 1939, the Polish high command took a far more realistic and pragmatic view of the situation than their British and French counterparts, who did not even bother to learn any of the lessons of the September campaign or make appropriate preparations, and were duly caught with their pants down the following year," he said.

AFP/Expatica