Producing security has long constituted a most important function, and perhaps the raison d' etre for the establishing of state which itself constituted the exclusive actor in the security domain. Today, however, the private military-security companies have transformed into the major actors in the security domain by engaging in conflicts, and playing various security roles alongside the state. As the demand for the activity of these companies has increased, not only they are increasing in number, but also the scope of their activities has expanded by adopting new roles and functions, so that today one might speak of a defense and security marketplace which includes two parts, namely those who supply and those who demand. Using a descriptive explanatory research method, the present research plans to address this question: “Why has the role and position of the private military-security companies been increased in security? ” The findings of the research indicate that globalization in political, economic and military dimensions contributes to the growth and deepening of insecurity in differing dimensions, the emergence of modern threats, and finally the redefinition of states, which have enabled the private military-security companies to play a wide and active role in security.