Mercenary

A mercenary, sometimes referred to as merc or soldier of fortune, is a soldier who participates in armed conflicts, often functioning as a third party, for private gain or material compensation. Historically, they were often hired by nations to take part in battles, or by private contractors to serve as personal protection.

They have no allegiance to either party, but they wage war for those who pay them the most. The prime target of a mercenary is safeguarding the assets of their client, like resources (oil, diamonds, mines) or to bring/keep people in power.