The year is 2610. Space exploration and colonization has become a reality. While humanity is still not united under any one government, progressive, international globalization has taken it's effect. The days of national superpowers like the United States and former Soviet Union have long past, for most Earth governments by this point have lost the overall authority they once held on a global scale. Now, following a slow rise in influence since the late 21st century, the United Nations is the dominant power in interplanetary politics.
But this newfound power is soon to be tested as civil unrest and overpopulation on Earth has led to the formation of radical new political movements promising change and independence from the national governments on Earth, in addition to the perceived "oppression" by the United Nations' colonial administration. Movements like the neo-communist Koslovics, who seek the complete removal of corporate and capitalist influence in the Sol system, and the facist secessionist Friedens, who believe that peace will only be achieved with the total elimination of it's "oppressors" on Earth, have already established themselves and have the resources and manpower to strike a massive blow to the United Nations. And between the growing momentum of these two movements, plus the countless other rebel factions that continue to spring up throughout human-occupied space, the United Nations' leadership have no doubt that all-out war not only in the colonies, but on Earth, is inevitable. So to meet these disillusioned rebels in battle, and to put a swift and decisive end to the war wherever and whenever it begins, the United Nations has formed a multinational rapid reaction force known as the Sol Rapid Reaction Fleet (SRRF), composed of crack military units from across the Earth.
You are the ranking officer of one such unit assigned to the fleet. The size, type and background of your unit will be left entirely up to you and could range from a small British commando unit to a battalion of mechanized Russian infantry. Or, if you're not much of a groundpounder, your command could range from a atmospheric/exoatmospheric strike fighter squadron to the entire crew of a state of the art warship. The choice will be yours, and as what will become known as the Interplanetary War progresses and more and more warzones prop up across the system, you may request more men be transferred out or to your command to combat what may turn out to be anything from overwhelming enemy infantry to unique combined arms formations.