One of my favorite little anecdotes about ancient mercenaries is that it was tradition for most of history to give your mercenaries two wages- "Bread" and "Gravy." Both were set at a daily value, but where "Bread" was intended to cover regular maintenance and life stuff and therefore paid out frequently (Here's your week's meal and gear repair budget!) the "Gravy" wage was paid out exclusively at the end of the contract as one lump sum. So like, your gravy wage and bread wage might be one silver coin per day each, so you're getting a handful of coins every week to cover food, and then at the end of an 800 day campaign, you get a wheelbarrow with 800 coins.
Employers liked offering this structure because then they didn't have to like, try to guess how long the invasion of spain will take and then carry 800 coins per soldier around the battlefield where it could be captured. It also gives them the chance to budget around the assumption that they take an enemy city and *find* vast sums of treasure even if they don't have the full value at the beginning of the war.
The main flaw of this system is that it's very easy to end up in a scenario where if you have, say, 50,000 guys that have been fighting for 800 days, you now owe 40 million silver to your army, and if the budget has not worked out to a 40 million surplus, you literally can't afford to end the war, but you can probably afford to pay them for a couple more weeks. So then you have to start thinking creatively.
Anyway across all time and history a lot of generals were ultimately beaten to death by men chanting gravy.
