Fortresses are . . . useful or not according to the times, and if they do well for you in one regard, they hurt you in another. And one may discuss the issue thus. The prince who has more fear of the people than of foreigners ought to make fortresses, but the one who has more fear of foreigners than of the people, ought to omit them. The castle in Milan built by Francesco Sforza has brought and will bring more war to the Sforza house than any other disorder of that state. Therefore the best fortress there is, is not to be hated by the people, because although you may have fortresses, if the people hold you in hatred fortresses do not save you; for to peoples who have taken up arms foreigners will never be lacking to come to their aid.