It's very historical and not at all unusual. Mercenaries only fought when paid - and on time. If payment was late or not at all, they stopped fighting your enemies. At best, because from that moment they started to focus on getting paid. Being in the business of violent enforcement and premeditated murder *(we call that 'war')*, they had ways to convince their paymaster rethink his sloppy payment policy. 

In Dutch and in German (probably in other languages too) there still is a proverb: "Geen geld, geen Zwiters" or in English: "No money, no Swiss". The Swiss were well known as excellent and courageous soldiers, as long as they were paid on time. The moment payment was late, they went on strike. 

It did happen mercenary bands changed sides, but that was bad for business. Their reputation was very important. Such a band would find it difficult to find future employment. 

Marching in a threatening way to the capitol, or wherever their employer happend to be, was (and is) a way to get what they want. 

[Mercenaries][1] are as old or nearly as old as the 'oldest profession in the world'. My answer focuses on Swiss and contemporary mercenaries, but the first mercenaries probably used their payment for services from aforementioned ladies. 

[Cretan archers][2] and [Balearic slingers][3] were famous and for hire.  

- [Geen Geld, geen Zwitsers][4] (Dutch)
- [Kein Geld, kein Schweitzer][5] (German)


  [1]: https://www.history.com/news/6-legendary-mercenary-armies-from-history
  [2]: https://en.wikipedia.org/wiki/Cretan_archers
  [3]: https://short-history.com/balearic-slingers-993b52917f44
  [4]: https://nederlandseofficierenvereniging.nl/geen-geld-geen-zwitsers/
  [5]: https://www.zitate-online.de/sprichwoerter/altvaeterliche/5809/kein-geld-kein-schweizer.html