[b]Private Military Contractors[/b]

In the latter years of the 20th century and toward the beginning of the 21st, private military contractors - Mercenaries - started to become more prominent or at least, more recognised. Private security firms existed across the world, but were more like security guards or at the most, close protection and body guards for VIPs and important persons, or security for sensitive or important corporate facilities; minimally armed and equipped. 
While Mercenaries had always been a part of the world throughout the ages these groups were more like the Armies for Hire of older years and days. Ex-military and military trained individuals, well-equipped with military grades firearms, vehicles and equipment. 
Mostly they plied their trade in Africa, South-East Asia and South or Central America and the Middle East; but more and more often they were involved in larger conflicts and even hired by governmental forces. 

Following the Heavenfall, these Private Military Contractors became more prominent and more important. With the global collapse of so many lines of communication, governance, supply and infrastructure as well as the widespread destruction of materiel, equipment and military infrastructure, conventional military forces were exhausted and over-stretched, and national attitudes were not eager to send more of their people off to far-off places to spend more money, capital and lives on poorly-understood goals and ideals, especially after so much destruction and on the tail-end of a ideological conflict they'd lived through for the last fifty years. 
Still needing to do something to secure policy, future interests, resources, and to protect regional allies and provide security in their regions, nations looked outward for new solutions - and the immediate one became the hiring of contractors to fight for them. 

These contractors would have to be as well armed and equipped as national armies were. They wouldn't be designed to replace them, or to take on every part of their role, such as providing long-term security and regional stability. Instead, they would be the tip of the spear, the first forces on hand, to carry out the immediate action. 
This was the case for the N/UN's planning for this new era of PMC's. They approached a number of extant PMC's, the most successful ones that also had good records of battlefield conduct and reliable information regarding them and the people who founded them and worked with them, and entered into a partnership agreement to provide them with additional resources, training, support and other necessary logistics. They would receive the same rates of pay, benefits, and support as national military forces, but operate under their own command structure, under contract to the N/UN, and receive legal protections - at least, under the N/UN, and any agreements between the N/UN and it's global allies. 
A number of PMC's signed up to the process, becoming 'Legitimate' or 'Authorised' PMCs, working worldwide for the N/UN and becoming a mobile, responsive and flexible array of forces at various scales and with various capabilities to carry out limited combat operations as a 'first strike' until larger forces from the N/UN could be bought to bear, or even working alongside such forces on occasion.

This increased presence and legitimacy of PMCs lead to more of them worldwide, as non-N/UN vetted PMC's also arose. Many of them were financed, supported and equipped by various MegaCorporations, acting as another source of revenue, as well as protecting their own interests and as advertising for their products in various combat zones. Others were formed and supported by the remains of shattered and broken state militaries, operating for their own self-interest or with some long-term goal, sending their payment back to their countries or territories of origin in an attempt to forge their own national identities. 

PMC's can range in size from a single unit or company of infantry operators, all the way up to an armoured vehicle company, or even a large air force. As well as combat operations, most PMC's also offer services such as training support, maintenance support, instruction and advisory roles, and other such non-combat, but combat-related services and utilities.