Be careful with military definitions. One near-universal aspect of a "profession" is that it be self-regulating. Lawyers have Bar Associations that dictate who can or cannot practice. Doctors have Medical Associations. So too accountants and engineers. These entities are granted monopolies but remain independent from government and set their own standards.
But by that definition, soldiering can never be a "profession" as a soldier is always regulated by the government they serve, and there is no professional association regulating mercenaries. But I would be very hesitant to suggest that the US Marines are not professional soldiers. They are. The definitions are messy.
But by that definition, soldiering can never be a "profession" as a soldier is always regulated by the government they serve, and there is no professional association regulating mercenaries. But I would be very hesitant to suggest that the US Marines are not professional soldiers. They are. The definitions are messy.