A war between two forts in the 16th century

may seem of little significance to us, but it was a very important event. It involved many thousands of men and women from both sides; armies marched over hundreds of miles through territory that had never been invaded before; they encountered people who were not prepared to be killed or enslaved by anyone, much less some foreign king. There was a lot at stake. The outcome would have profound implications for the future of Europe.

And yet there's no record anywhere about what happened during this conflict. No one wrote down an account of it, no historian recorded the events, no artist painted a scene of battle. There are only occasional references to it scattered here and there across the centuries, but nothing that explains exactly what went on.

It's really quite strange. If you look at the wars fought in Europe over the last couple of thousand years, you'll find plenty of records of battles and sieges: Roman legions marching up against the Saxons, the Norman knights fighting the English king at Hastings, the French and Spanish navies bombarding the British Isles in the seventeenth century. But these are all detailed accounts of actual conflicts with clear victors and losers – and we know how those wars turned out (the Romans defeated the Saxons, the Normans conquered England). Yet when it comes to the Thirty Years War, nothing is known except that the Germans won.

That's because the Thirty Years War didn't happen. Or rather, it did happen, it just wasn't reported as such. In fact, it was probably the biggest war ever fought between European states, bigger even than the Thirty Years War itself.

But it doesn't exist. Because it never happened. Not according to any official records.

The Thirty Years War began in 1618, when Charles I became King of Bohemia after the death of his father, Rudolph II. The following year he married Sophia Dorothea, Duchess of Lorraine, which gave him control of her vast estates. He was soon embroiled in a war with Spain, and when the Spaniards captured Namur in western Belgium in 1619, the Thirty Years War began as a series of minor skirmishes.

By 1620, however, the war had reached its peak intensity. The Spanish army had advanced into Germany, while the Duke of Lorraine led an army into France. The Swedes and the Dutch joined them, and together they fought their way north towards Brussels. From there they could attack the German heartland, where the greatest concentration of power lay.

At this point, a new player entered the game. A young man called Gustavus Adolphus, King of Sweden, decided to take advantage of the chaos created by the warring factions. In July 1621 he landed in Hamburg, and then marched across northern Germany, reaching Berlin in October. Within a few weeks, Sweden's army controlled much of central and eastern Germany. At the same time, Charles' army was being steadily pushed back towards France. The Dutch, meanwhile, were fighting a losing battle against the Swedes in the Netherlands.

In the midst of this confusion, Gustavus Adolphus realized that he now held the decisive card. He gathered his army around him and rode south, towards the heart of the conflict. By springtime he was marching towards Leipzig, the capital of Saxony.

There, the Thirty Years War came to a sudden end. On 20 April 1632, Gustavus Adolphus faced off against the Imperial commander, Prince Maurice of Saxe-Weimar, in the Battle of Breitenfeld.