Mercenary

A mercenary is a person who takes part in an armed conflict who is not a national or a party to the conflict and is "motivated to take part in the hostilities by the desire for private gain". In other words, a mercenary is a person who fights for personal gains of money or other recompense instead of fighting for the ideological interests of a country, whether they be for or against the existing government. In the last century, and as reflected in the Geneva Convention, mercenaries have increasingly come to be seen as less entitled to protections by rules of war than non-mercenaries. However, whether or not a person is a mercenary may be a matter of degree, as financial and national interests may overlap.

https://en.wikipedia.org/wiki/Mercenary