A separate office was devoted to his correspondence, of all of which he kept accurate copies.[1] By applying this mercantile machinery to the management of his vast dominions, at a time when public economy was but little understood in Europe, Gian Galeazzo raised his wealth enormously above that of his neighbors.

His income in a single year is said to have amounted to 1,200,000 golden florins, with the addition of 800,000 golden florins levied by extraordinary calls.[2] The personal timidity of this formidable prince prevented him from leading his armies in the field.

He therefore found it necessary to employ paid generals, and took into his service all the chief Condottieri of the day, thus giving an impulse to the custom which was destined to corrupt the whole military system of Italy.

Of these men, whom he well knew how to choose, he was himself the brain and moving principle.

He might have boasted that he never took a step without calculating the cost, carefully considering the object, and proportioning the means to his end.