There are quite a few good stories about the invention of panforte. Myths are what they are, but they’re a little weirder and/or more creative than the typical Pope-coming-to-dinner narratives you encounter with Medieval foods. Many involve a nun by the name of Sister Berta who is said to have lived sometime around the 13th Century in, of course, Siena.
The first story unfolds in the aftermath of a siege of the city. Sieges being what they are, supply lines were cut off for months. Eventually it ended (Siena evidently won), but once the jubilation wore off, Berta began to notice how emaciated the Sienese inhabitants looked. Diving into her stores of nuts and dried fruits, she created a compact, long-keeping high energy food. The locals called it “panforte” because it made them strong, and Berta went on to become the patron saint of the highly profitable nutritional/snack/energy bar category. OK, I made that last bit up. But then the whole thing is made up. What kind of nun hoards fruits and nuts during a siege, only to give them out later when it’s over?
Another hole in the story is the fact that Siena was not besieged around that time, although it was involved in a short war against its much larger and wealthier regional rival, Florence. What did those two city-states have to fight about? For one, they were economic competitors, both were involved in trade and lending. For another they had fundamentally opposing political systems. Siena was a commune while Florence was ruled by a merchant oligarchy. But the icing on the hate cake was that the Florentines were Guelphs and the Sienese were Ghibelines, which means one population was allied with the Pope, the other to the Holy Roman Empire. I’ll bet you can guess who supported who.
Tensions finally came to a head in 1260 when an army of 33,000 Florentines marched on Siena. They were met near a large hill called Montaperti by a force of 20,000 mostly-Sienese troops, supplemented by some like-minded Sicilians. It should have been an easy victory for Florence. The problem was that the Florentines, in a freakish friendly fire incident, took out their own standard-bearer. Why was that a problem? Because no one wore military uniforms or insignia in those days. Without a standard-bearer the Florentine troops had no way of knowing where their lines were, where their leadership was or what they wanted them to do. Chaos ensued and the Florentines were routed.
To this day Siena doesn’t let the Florence forget it. In any competition, be it a soccer match or a friendly game of bocce, the trash talk from the Sienese side is always “Remember Montaperti!”