s
tyranny, he dreaded the personal eminence of his generals above all
things. His chief object was to establish a system of checks, by means
of which no one whom he employed should at any moment be great enough to
threaten him. The most formidable of these military adventurers,
Francesco Sforza, had been secured by marriage with Bianca Maria
Visconti, his master's only daughter, in 1441; but the duke did not even
trust his son-in-law. The last six years of his life were spent in
scheming to deprive Sforza of his lordships; and the war in the March,
on which he employed Colleoni, had the object of ruining the
principality acquired by this daring captain from Pope Eugenius IV. in
1443.

Colleoni was by no means deficient in those foxlike qualities which were
necessary to save the lion from the toils spread for him by Italian
intriguers. He had already shown that he knew how to push his own
interests, by changing sides and taking service with the highest bidder,
as occasion prompted. Nor, though his character for probity and loyalty
stood exceptionally high among the men of his profession, was he the
slave to any questionable claims of honor or of duty. In that age of
confused politics and extinguished patriotism, there was not indeed much
scope for scrupulous honesty. But Filippo Maria Visconti proved more
than a match for him in craft. While Colleoni was engaged in pacifying
the revolted population of Bologna, the duke yielded to the suggestion
of his parasites at Milan, who whispered that the general was becoming
dangerously powerful. He recalled him, and threw him without trial into
the dungeons of the Forni at Monza. Here Colleoni remained a prisoner
more than a year, until the duke's death, in 1447, when he made his
escape, and profited by the disturbance of the duchy to reacquire his
lordships in the Bergamasque territory. The true motive for his
imprisonment remains still buried in obscure conjecture. Probably it was
not even known to the Visconti, who acted on this, as on so many other
occasions, by a mere spasm of suspicious jealousy, for which he could
have given no account.

From the year 1447 to the year 1455, it is difficult to follow
Colleoni's movements, or to trace his policy. First, we find him
employed by the Milanese Republic, during its brief space of
independence; then he is engaged by the Venetians, with a commission for
fifteen hundred horse; next, he is in the service of Francesco Sforza;
once m