War Was Made to Pay for Itself Through Pillage
…Raising money to pay the cost of war was to cause more damage to 14th century [C.E.] society than the physical destruction of war itself. The governing fact was that medieval organization by this time had passed to a predominantly money economy. Armed forces were no longer primarily feudal levies serving under a vassal’s obligation who went home after forty days; they were recruited bodies who served for pay. The added expense of a paid army raised the cost of war beyond the ordinary means of the sovereign. Without losing its appetite for war, the inchoate state had not yet devised a regular method to pay for it. When he overspent, the sovereign resorted to loans from bankers, towns, and businesses which he might not be able to repay, and to the even more disruptive measures of arbitrary taxation and devaluation of the coinage.
Above all, war was made to pay for itself through pillage. Booty and ransom were not just a bonus, but a necessity to take the place of arrears in pay and to induce enlistment. The taking of prisoners for ransom became a commercial enterprise. Since kings could rarely raise sufficient funds in advance, and collection of taxes was slow, troops in the field were always ahead of their pay. Loot on campaign took the place of the paymaster. Chivalric war, like chivalric love, was, as Michelet said of the whole epoch, double et louche (a provocative phrase which could mean “double and squinting” or “equivocal” or “shady” in the sense of disreputable). The aim was one thing and the practice another. Knights pursued war for glory and practiced it for gain.
— A Distant Mirror, p. 84