Watching Yevgeny Prigozhin’s rebellion unfold last week, it was hard to avoid feeling that Vladimir Putin should have paid more attention to Machiavelli’s Prince when he was in school. If he had, he’d have known that any ruler who stakes his power on mercenaries is making a big mistake. For mercenaries, Machiavelli wrote, are ‘disunited, ambitious, undisciplined, [and] disloyal; valiant among friends, among enemies cowardly; they have no fear of God, no loyalty to men’. At best, if they are led by a fool, they merely ruin you; if their commander is even remotely worth his salt, he invariably ‘tries to gain power’ for himself, ‘either by harassing you’, or by interfering in your plans in some other way.

Machiavelli knew what he was talking about. Back when he was second chancellor of the Florentine Republic, in the early sixteenth century, mercenaries dominated the practice of war in the Italian peninsula. Organized into large bands, under the command of a general known as a condottiere, they had come to the fore over the past two hundred years in response to growing scale of armed conflicts, and the development of new weapons, such as the crossbow, which required specialised training. By around 1500, states like Florence had come to rely on mercenaries almost to the exclusion of anything else.

Their advantages were undeniable. They were heavily armed, highly professional, and often very experienced. During the later fourteenth century, many were foreign veterans, who had previously fought in the Hundred Years’ War, or served in the armies of Henry VII of Luxembourg and his son John of Bohemia. They were also extremely flexible. Since they were hired on a contract basis, states could employ as many – or as few – as they needed, for specified periods of time, ranging from a couple of months to a few years. When the contracts expired, the terms could always be renegotiated; and new bands could always be hired in the middle of a campaign, if the need arose.

They could be good at defending their employers, too. In fact, some states were so grateful for their service that they commemorated their generals with public memorials. In 1436, Paolo Uccello was commissioned to paint an equestrian portrait of the English condottiere Sir John Hawkwood on the walls of Florence cathedral. A few years later, the Republic of Venice erected a bronze statue of Erasmo da Narni (‘Gattamelata’) in the Piazza del Santo in Padua.

But Machiavelli knew only too well that mercenaries were a troublesome breed. For one thing, they were extremely expensive. Equipment, supplies, and logistics always cost a lot; and mercenaries, conscious of their own value, usually demanded a high price. This placed a heavy burden on public finances. One of Machiavelli’s earliest works is a speech, meant to be given by the head of Florence’s government, on the need to increase taxes to pay for more soldiers. But taxes could only be raised so far and, as a result, the cost of mercenary armies often pushed many states to the point of bankruptcy.

They were also undisciplined. In the Art of War, Machiavelli recalled that, since mercenaries did not know ‘how to live by any other occupation’, they often resorted to robbery – as well as every other manner of abuse. Through the character Fabrizio Colonna, Machiavelli dolefully asked:

When will they abstain from gaming, from whoring, from cursing, from the outrages they daily commit? When can they be brought back to such discipline and such obedience and respect that a tree full of apples can stand in the middle of the camp and be left untouched?

Rape, murder, and kidnapping were depressingly common, especially on campaign. Sometimes, not even their commanders could control them. In March 1527, Georg von Frundsberg had a stroke while trying (ineffectively) to remonstrate with Swiss landsknechts who were angry about being denied the booty they had been promised. Less than two months later, they sacked Rome.

This could have a devastating impact on local populations, of course. But, on occasions, it even interfered with mercenaries’ military objectives. In the Istorie fiorentine, Machiavelli noted that, in 1439, Niccolò Piccinino lost Verona simply because his soldiers were too busy robbing the place.

More troublingly, mercenaries could be alarmingly cowardly. Although they were paid to fight, there was more incentive for them not to. Fighting was, after all, a dangerous business, even for a professional. If they got wounded, they would not be able to earn their bread. And if they died, so much worse. They preferred simply to march around the countryside, avoiding the enemy as much as possible, sometimes even by agreement. As Machiavelli put it in the Istorie fiorentine, ‘these men … turned war into a technique for wasting so much time that when two states made war, both of them generally lost’.

Worst of all, mercenaries were often disloyal. Conscious that states such as Florence were dependent on them, they often exploited this fact for their own benefit. There are countless examples of condottieri refusing to fight unless they were given more money, or even switching sides when it was in their interest. In the fourteenth century, for example, Hawkwood had been bribed to abandon the pope and fight for the Florentines instead; but when peace was declared, and he found himself unemployed, he ravaged the countryside until Florence agreed to renew his contract, for even more pay. Even more strikingly, in the fifteenth century, Francesco Sforza ‘not only deceived the Milanese by whom he was employed, but took away their liberty and became their prince’.

It is hardly surprising that Machiavelli blamed mercenaries for Italy’s ills – or that he became such an outspoken advocate of a citizen militia. Even if farmers and shoemakers made less proficient soldiers, Machiavelli believed, they were still likely to defend their patria more faithfully and respect the rule of law more assiduously – and that was surely what really mattered.

But even Machiavelli realised that it was difficult to live without mercenaries. Though the diarist Luca Landucci thought his militia ‘the finest thing ever organised by the city of Florence’, it was difficult to raise enough men, quickly enough to do without them altogether. How then, did Machiavelli think troublesome mercenaries should be dealt with, if the state was not to be endangered?

The answer was simple: ruthlessly. If a condottiere revolted, or was even suspected of revolting, he could not be allowed to live. Forgiveness breeds no greater fidelity; and mercy only emboldens further rebellion. In 1499, Machiavelli had been present when the Florentine government had executed the mercenary general Paolo Vitelli, without a shred of evidence that he had done anything wrong, simply pour encourager les autres; and three years later, he had watched with amazement as Cesare Borgia had surprised, imprisoned, and killed his rebellious captains at Sinigaglia. Granted, this was cruel. But it was effective; and, as Machiavelli pointed out in The Prince, no ruler should worry about cruelty if it leaves his state safer and his government more secure.

Whether Putin will regret not following this advice remains to be seen.