The Art of War is the only one of Machiavelli's major political books published in his lifetime, and it argues the case The Prince assumes: that a state which relies on mercenaries is defenceless, and that a citizen militia is the only reliable foundation of power. The Prince states the conclusion as a rule for a ruler; the earlier book is where it is worked out, drawing on Roman practice and on Machiavelli's own attempt to raise a Florentine militia. The relationship runs the other way from the publication dates, which is why the claim rests on the composition order rather than on the printing.