For an artist whose designs, more often than not, failed to seep down from the conceptual to the material realm, Leonardo must have found Ludovico's steady court stipend reassuring. Not wishing to disappoint his sponsor, Lorenzo, or Sforza (as he had Ser Piero), Leonardo was willing to play almost any role asked of him at the Milanese court. No design or engineering project was too minor, be it a belt buckle, a drainage ditch, or a water-driven gadget for the “bath of the Duchess.” Certainly, under the penetrating glare of Il Moro, Leonardo had to keep himself constantly busy and could not revert to some of his bad habits of youth. Watching over Leonardo, too, were – still affixed to a bell tower – the heads of those responsible for the murder, six years earlier, of Ludovico's brother, Galeazzo Maria. The exceptional, creative cruelty of Il Moro and Galeazzo Maria, who once had a man nailed alive to his own coffin, cast an apprehensive pall over all of Milanese life.

Leonardo had accepted as his new patron a man whose enormous power, energy, and artifice equaled his malevolence. Declared by the political expert Nicolò Macchiavelli to be responsible for the “ruin of Italy,” the treacherous Ludovico Sforza summoned Charles VIII of France to Italy to aid him militarily. Bankrolled in part by Il Moro, the French king and an army of forty thousand men subsequently marched down the length of the Italian peninsula in 1494, leaving untold destruction and atrocities in their wake, to claim French sovereignty over the Kingdom of Naples. Meanwhile, Sforza quickly dispatched with the Milanese secretary of state and anyone else who, he thought, might undermine his authority. Not coincidently, by October of that year, Ludovico's nephew, Duke Gian Galeazzo Sforza had taken ill. Most suspected he had been poisoned. Upon Gian Galeazzo's death, Il Moro had his widow and children arrested and imprisoned, and proclaimed himself Duke of Milan.