It has been nearly two decades since the international community first focused significant attention on the private military firm as an important actor in conflict. Although quasi-firms and groups of individuals had operated in conflict zones before, a series of high-profile interventions by private military firms in the 1990s served as a watershed moment for the private security industry. In particular, the positive changes to the security environment brought about by private military firms in Angola (1992-1995), Sierra Leone (1995-1999) and Croatia (1994-1996), combined with newfound claims for the firms' legitimacy as security actors, made the world sit up and take notice.
The market for private military firms emerged at that time due to a combination of factors. These included post-Cold War disorder; the fragility of many developing states when they lost their superpower backers; the unwillingness of those backers to intervene in certain parts of the world now that the geostrategic situation had changed; the willingness, by contrast, of some private corporations to pay for operations to secure their valuable natural resources; the international urge to realize a "peace dividend" by reducing the size of military forces and by privatizing services; and the resulting ready supply of demobilized soldiers and plentiful weapons (pdf). At a time when the international appetite for intervention, even in the name of peacekeeping, was low, these private military firms stepped into the vacuum.
Some of these pioneering private military firms (PMFs) of the 1990s met with a firestorm of opposition to their activities. In particular, Executive Outcomes and Sandline International, firms that were actively engaged in the African conflicts mentioned above, were at times praised but more often condemned for their actions. Both of these firms subsequently closed down: Executive Outcomes, which dissolved in 1999, was targeted by legislation that hampered its operations; Sandline International was eventually brought down by scandal in April 2004, a month after its co-founder Simon Mann was arrested in Zimbabwe for attempting to stage a coup d'etat in Equatorial Guinea. Of the early pioneers, only Military Professional Resources Incorporated (MPRI), which trained the Croatian military during the Balkan wars, survives and prospers.