Does anyone know any facts about mercenaries?

Answer 1

Soldiers for hire predate standing armies.

The term "company" as a military unit is derived from the "free companies", which were mercenary armies during the late medieval period.

In 1991, the UN Mercenary Convention was passed, in which mercenaries would from then forth be considered illegal combatants under international law.

In the case of American contractors working for PMCs in places such as Iraq and Afghanistan, the contractors are not considered mercenaries by law because they are nationals of a party to the conflict.

The infamous Caribbean pirates were original raiders for hire by the various governments warring for control of trade in the region. They were known as privateers, and hired to conduct raids against enemy shipping, essentially making them mercenary sailors.