The earliest known unmanned aerial attack actually took place in the mid-19th century. In the summer of 1849, during which Venice was involved in a brief revolt against Austrian rule that established the Venetian Republic one year prior, the Austrians had the city under siege. In an attempt to force a surrender, the Austrians tried using balloons in a new way 66 years after the French made use of large-scale hot air balloons for manned flight. The Austrians loaded up unpiloted balloons with explosives, launching several from the ship Vulcano. The balloons, each about 23 feet (5.7 meters) in diameter, were armed with bombs, possibly triggered by timed fuses or other electrical activation method, and released in favorable winds in the direction of Venice. Once triggered the balloon dropped its small load of bombs, which then exploded upon reaching the ground. It was reported that some of the balloons operated as planned, dropping bombs over the city, but several were blown back over Austrian lines. The ultimate impact on the siege was likely small, and ultimately the Venetians agreed to surrender on August 22, 1849.
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