In the summer of 1515 during the Revolution in Military Affairs known as the Italian Wars, France’s Francis I crossed the Alps at the head of 30,000 troops in a feat comparable to Hannibal’s crossing 1600 years before. Francis’ bold movement over an inadequate, treacherous, and unguarded pass completely unhinged the Papal/Swiss/Imperial/Spanish defenses and they fell back to Milan.

Like his grandfather Charles VIII, who seized the Kingdom of Naples, and every French King since the fall of the Roman Empire, Francis saw the Italian peninsula as his political playground. He desired Milan for some overly complicated scheme, and his French gendarmes (knights), cannon, and German Landsknechts (pike and halberd armed mercenaries) lined up outside the city to begin a siege. On 13 September 1515, just outside of the ruins of the village of Marignano, Duke Sforza of Milan attacked the French with three massive columns of Swiss pikemen.

The battle was fought for 28 hours over the 13th and 14th. The Swiss routed the landsknechts on Francis’ left but they rallied, and held the baggage train with the camp followers in an impromptu wagon fort. On the French right the Swiss and Germans were locked in bloody stalemate between pike phalanxes that would not have been out of place in the Diadochi Wars after the death of Alexander the Great. The center was destined to be decisive.

In the center, a Swiss “Forlorn Hope” (there’s a docturnal term we need to bring back, it’s essentially an initial attack by a body of troops that expects to either die or gain great glory in the initial charge) quickly seized the French siege guns. But before they could destroy them, the forlorn hope was massacred by a charge of the Gendarme led by Francis himself, and The Black Band, a group of halberd and arquebus armed German mercenaries intensely loyal to Francis. As the Swiss main body approached, Francis ordered the cannon, which he brought to fire on the walls of Milan, to fire on the Swiss phalanxes. The halberdiers and arquebusiers fixed the Swiss, the cannon broke up the Swiss formations, then the gendarmes charged into the chaos. However, the charge was not decisive. Inevitably, the Swiss would reform and attack again. This cycle continued for the rest of the battle. Francis himself took part in 30 charges over 24 hours. On the afternoon of the 14th, the Swiss finally broke when a Venetian army of condottieri (mercenaries), allies of the French, appeared on their flank.

At the time, the Battle of Marignano was considered a triumph of the armored knight. But in actuality it was the knight’s last hurrah, and signaled the coming of age of cannon. Marignano was the first large scale use of cannon against troop formations, and the battle was the first example of cannons’ use in combined arms warfare in a modern sense. Finally, after the battle, the Swiss signed an agreement of “Eternal Peace” with the French, which began the Swiss tradition of neutrality in all world affairs, which holds to this day.