I've started reading Carlo Goldoni's play titled La guerra ('The War'). I haven't found any translation into English. One of the characters is Don Polidoro, the war commissioner. He praises war greatly because he expects to make significant profits and become very rich from it. In fact, from the first act, this character declares that he will always speak well of war and will never desire peace because at that moment he is already swimming in abundance thanks to the great business that wartime represents for him as a commissioner. There are several other characters who are certain that commissioners get rich thanks to the war. For example, in the Second Scene of the First Act, the ensign Don Faustino says:
La casa di un commissario di guerra è il fondaco dell'abbondanza. L'oro che consumasi nelle armate, non si perde sotterra; cola nelle mani di alcuni particolari, e i commissari ne hanno la maggior parte.
I'll try to translate it into English:
The house of a war commissioner is a store of abundance. The gold consumed in the armies doesn't vanish into the ground; it flows into the hands of a few individuals, and the commissioners have the largest part of it.
Some informations about this play can be found in Goldoni's Mémoires, which the author wrote in French:
La vue de Parme m'avait aussi rappelé à la mémoire la bataille que j'y avais vue en 1746, et pour varier les sujets de mes, comédies, je composai une pièce intitulée la Guerra (la Guerre).
L'action principale de cette pièce est le siége d'une forteresse, et le lieu de la scène est tantot au camp des assiégeans, et tantot dans la place assiégée.
[...] Le tableau de l'armistice tracé d'après celui que j'avais vu au siége de Pizzighitone, [...]. [...].
Je ne traite pas trop bien un commissaire des guerres qui avançait de l'argent aux officiers avec un intérèt proportionné aux dangers de la guerre. J'eus tort, peut-être, mais je n'avais rien fait de ma tête. On m'en avait parlé, on me l'avait montré, et je lai mis sur la scène sans le nommer.
My translation:
The view of Parma also brought back to my memory the battle that I had seen there in 1746, and to vary the subjects of my comedies, I composed a play entitled la Guerra (The War).
The main action of this play is the siege of a fortress, and the location of the scene alternates between the besiegers' camp and the besieged place.
[...] The representation of the armistice drawn from the one I had seen at the siege of Pizzighitone, [...]. [...].
I did not treat very well a war commissioner who advanced money to officers with interest proportional to the dangers of war too kindly. Perhaps I was wrong, but I had not thought of it myself. People had talked to me about it, they had shown him to me, and I put him on the stage without naming him.
So, according to the informations of the website of the event Pizzighettone fra XVI e XVIII secolo (Pizzighettone from the XIV to the XVIII centuries), the context of the play is that of the War of the Spanish Succession between the Habsburgs and the Bourbons:
Occupato dalla fazione borbonica nel 1701, lo Stato di Milano divenne campo di battaglia per gli eserciti dei due parti contendenti. Nell'autunno 1706 la piazzaforte di Pizzighettone fu assediata e conquistata dalle truppe congiunte degli Asburgo e dei Savoia, capitanate dal principe Eugenio di Savoia-Soissons (1663-1736).
My translation:
Occupied by the Bourbon faction in 1701, the Duchy of Milan became a battleground for the armies of the two contending parties. In the autumn of 1706, the fortified town of Pizzighettone was besieged and captured by the joint forces of the Habsburgs and the Savoy, led by Prince Eugene of Savoy-Soissons (1663-1736).
I don't know what the role of a war commissioner was in the 18th century. That's why my question is: why was it assumed that a commissioner would become wealthy through war?