DON’T try on that fez. During the world’s longest siege, a 17th-century scientist hatched an ambitious plan – to weaponise the bubonic plague by painting it onto hats.

The plot, which has just come to light, was discovered by Eleni Thalassinou at the University of Athens in Greece and her colleagues in six letters sent between 1649 and 1651. During that time, the town now known as Heraklion in Crete was under Venetian control but besieged by Ottoman troops.

Michiel Angelo Salamon, a doctor in what is now Croatia, had an idea. The letters, sent between the rulers of the Venetian empire and the governor of a Croatian outpost, detail Salamon’s scheme for harnessing the plague, the deadly infection that swept across Europe in 1348 and had been circulating there ever since.


Salamon appears to have devised a method for distilling the essence of plague. “He availed himself of the presence here of the plague to distil a liquid expressed from the spleen, the buboes and carbuncles of the plague stricken,” wrote the governor of Zara (Historical Review, doi.org/9fs).

The governor proposed painting this liquid onto goods that besieging Turks were likely to buy – such as hats known as Albanian fezzes.

“The governor proposed painting liquid expressed from carbuncles onto goods for the besiegers”

Such a plan reflects people’s understanding of the plague at that time: that it spread from person to person, and could be transmitted through cloth contaminated by bodily fluids.

The Venetian authorities were enthusiastic, but insisted Salamon personally oversee his plan – which he reportedly agreed to with “great unwillingness”. However, we do not know whether he ever executed his scheme because the letters end in 1651.

But if he did, it didn’t succeed. The Ottoman siege lasted another 18 years. Today, we know that the plan was unlikely to have worked. In 1844, historians proposed that the Black Death was a bacterial disease called bubonic plague carried by rodent-borne fleas. Salamon kept his jar of plague potion for several years, by which time any bacteria it contained would have died.

Salamon’s plot wasn’t the first biological warfare plan based on a limited understanding of how diseases spread. Earlier medieval tactics included throwing rotting carcasses over the walls of besieged towns in the belief that bad smells could spread disease. Historical accounts suggest this did sometimes work, according to research by Mark Wheelis of the University of California at Davis, either by actually spreading germs, or just by making a place stink too much to remain there.

Later would-be biowarriors turned to smallpox. Documents from 1763 show that British commanders gave blankets and a handkerchief from smallpox victims to Delaware Indians, intending to spread the disease, although it is not clear if they succeeded.

But at least one siege does seem to have been broken by using bioweapons. In 1776, British troops managed to end the American siege of Quebec by innoculating prostitutes with smallpox and sending them out of the city. Unlike later vaccines, this early method also transmitted the disease.

(Image: Christie’s Images/Corbis)

This article appeared in print under the headline “Renaissance rulers plotted biowar with hats”

Correction:Since this article was first published, the date on which it was proposed that the bubonic plague had a bacterial cause has been changed.