A mercenary is a hired professional who has been trained to fight for any state or nation without any political interests except for money or personal interest. Mercenaries have been existing since the early years.
During the hundreds of years of wars, Europe was overrun with men who were only trained in fighting, and also during the free companies of Swiss, Italian, and German, the mercenaries sold their service to a lot of dukes and princes. In the late 18 century, mercenaries won some prominence in the third world II and also, in Africa, they were hired by government and anti-government organizations.
It was later declared by the Geneva Convention that mercenaries are not recognized as legitimate combatants, and they do not have any legal protection. Examples of mercenaries include the joseph Adams, George bacon, Charlie Christodoulou, Yves Debay, Perter McAleese.