Explanation: In the civil war of the Roman politician and conqueror Julius Caesar during the Late Republic, the Legions he had raised and fought with over long years in Gaul were fiercely loyal to Caesar and his cause. At an early point in the war, his troops vowed to serve without pay (as a temporary measure) and donated money from their own savings (kept with the Legion standards for safety’s sake, like a military bank) to fund the raising of additional troops for Caesar’s cause. They also volunteered to pay for each other’s supplies for the duration of Caesar’s financial shortage, with the richer men providing for the poorer. This was because Caesar, cut off from his contacts in Rome by the outbreak of the civil war, effectively had very little in the way of resources to call on until he could wrest support and access to Italy.

While the troops had a bit of a ‘do or die’ situation facing them, as following Caesar to begin with meant that losing and thus being branded traitors would be… disastrous for them, personally… Caesar also had several other attributes which attached the men of his Legions to him. Caesar was noted as extremely charismatic - with the conservatives in the Senate even taking measures to prevent him from meeting personally with moderates during the negotiations leading up to the civil war, for fear that he might persuade them to support a compromise.

Notably, despite being something of a notoriously vain dandy who was always up in the latest fashions (even when the fashion was regarded as ‘effeminate’) and had his body hair regularly plucked, and was a man with immense cultural and artistic sense, on the campaign trail, he was noted as living in the same rough conditions as his men. Troops love a commander who is ’one of them’, and willing to share in their hardships and ask no more of them than he would of himself. Caesar was also notably brave in personally exposing himself to danger in battle, and calm in combat, which soldiers often find reassuring.

He was also famously generous and gregarious, always seeking to reward loyalty, make friends, and with a remarkable memory, sometimes being remarked as knowing many or even all the centurions (commanders of ~80 men) in a given legion (~4800 men) by name. Despite his immensely high opinion of himself, he had a way of appearing welcoming and egalitarian even to social inferiors, and enforcing that standard on his officers and allied politicians - a good talent for any leader to cultivate! Caesar once, supposedly, said that he would reward even a bandit, if the bandit had done him a good turn. Because of this attitude of reliable reciprocity, the legionaries probably felt fairly certain that their loyalty to Caesar would be rewarded - and true to Caesar’s reputation, it would indeed be rewarded at the end of the civil war, with promotions, honorable discharges, money, land, and for some of the higher-ranking troops, support for political offices.

Funny enough, there are numerous examples of the early Imperial-era Legions acting against their own material interests. But as the Empire’s core legitimizing myth of Rome remaining a semi-democratic semi-functional city-state faded (THE EMPEROR IS JUST A REALLY POWERFUL REPUBLICAN MAGISTRATE WE SWEAR), and the stability of the Empire declined with increasingly arbitrary and ruinous Emperors, with the 3rd century AD in particular standing out for ever-escalating bribery and decay of the Empire in general and the Legions in particular. By the 4th century AD, the Legions as they were at the height of the Empire in the 1st and 2nd century AD no longer existed, save as the occasional relict unit name.

Those 4th century and 5th century AD troops sure as shit weren’t about to donate their limited resources to some abstract cause when their own wages weren’t delivered half the time, despite their leaders living with disgusting wealth! Fuck you, pay me!