Pisa becomes independent and a free republic. The Florentines fail to breach Pisa’s walls, nor even block its trade, as the Arno River provides access to the sea. Columbus has just returned from the Americas, and a few years later, Amerigo Vespucci will also return from Brazil. Amerigo Vespucci’s cousin, among other things, had worked with Machiavelli in Florence in the republic’s chancellery. The Americas make it more urgent for Florence to regain control of Pisa and its access to the sea. In July 1503, Leonardo da Vinci is asked to divert the Arno River upstream to leave Pisa dry and give Florence access to the sea. Machiavelli is also in favor of the idea. Leonardo plans everything in detail, but the execution is inadequate, and the project fails.
