An anecdote from Luca Pacioli's _De viribus quantitatis_ relates an incident with Leonardo da Vinci in his capacity as military engineer on campaign with Cesare Borgia.
> One day Cesare Valentino, Duke of Romagna and present Lord of Piombino, found himself and his army at a river which was 24 paces wide, and could find no bridge, nor any material to make one except for a stack of wood all cut to a length of 16 paces. And from this wood, using neither iron nor rope nor any other construction, his noble engineer made a bridge sufficiently strong for the army to pass over.
Extract from a dispatch of Machiavelli to the Signoria of Florence concerning Cesare Borgia:
> This Duke is so enterprising that nothing is too great to be discounted by him. For the sake of glory and the enlarging of his dominions, he deprives himself of rest, yielding to no fatigue, no danger. He arrives in one place before anyone knows he has left the other, he gains the good will of his soldiers, he attracts to him the best men in Italy, and he has constant good luck. For all these reasons he is victorious and formidable.
Passport drawn up in Pavia granting Leonardo da Vinci free access to the dominions of Cesare Borgia as his chief military architect:
> Cesare Borgia of France, by the grace of God Duke of Romagna and Valence, Prince of the Adriatic, Lord of Piombino etc., also Gonfalonier and Captain General of the Holy Roman Church: to all our lieutenants, castellans, captains, _condottieri_, officials, soldiers and subjects to whom this notice is presented. We order and command that the bearer thereof, our most excellent and well-beloved architect and general engineer Leonardo Vinci, who by our commission is to survey the places and fortresses of our states, should be provided with all such assistance as the occasion demands and his judgement deems fit.
Extract from a dispatch of Machiavelli to the Signoria of Florence while in the service of Cesare Borgia:
> This morning Messer Rimino was found lying in the piazza cut into two pieces; he still lies there, so that everyone has had an opportunity to see him ... The reason for his death is not yet clear, except that such was the pleasure of the Prince, who shows is that he can make and unmake men according to their deserts.
Cesare Borgia (son of Pope Alexander VI) occupies Urbino, where he imprisons two potentially treacherous allies, Vitellozzo and Oliveretto; he executes them the next morning.