Before mankind reached out and took his place among the stars. Before we met the first alien races. Before we collectively took those first tentative steps outside our solar system…
Mankind brought itself to the brink of Apocalypse.
The balance of power had shifted. Earth no longer had a single dominant power vying for control. Nations were poised to grab for the top spot, and had the weapons to eliminate their competitions many times over, each ready to issue the retaliatory strike.
Enter the corporations.
Some striving for control of the governments of Earth, others leading the way in technological and biological advancements and others still tasked with military research all of them had a vested interest in a non-nuclear solution. The corporations soon began to run their own operations. Covert at first, their missions soon became the norm, ranging from corporate espionage to full on military actions. Since they were operating as mercenary agents, the patron nations had a scapegoat to point at when politics became volatile thereby avoiding major tactical responses. The corporations had found new revenue streams. It was a win-win situation.
At least until the corporations realized who actually ran 
things…