That element of coercion comes up again and again in the armies of kings and imperial cities. There are letters from British settlers in India saying “look, what am I supposed to do with this shipload of Scots you sent me, half of them are bent and lame, three quarters have never touched a musket before and the ones with any fight in them would rather knife each other than the enemy.”
‘Mercenary’ is a term used by moralizing rich and romantic nationalists. People who didn’t have to work insulted people who could only fight if someone paid them; romantic nationalists objected to anything which might stop people from throwing themselves into the gunfire for the nationalists’ dreams. Its always my eager volunteers but your slavish hirelings, my allies and your foreign combatants. Those old Edwardian historians like Sir Charles Oman got very indignant that when the money runs out the Swiss walk out, but what was the alternative? Did they think that if some Swiss pikeman had a leg shot off, the kind of people who hired him would promptly pay his back wages and a nice pension?