In the first book the main character joined the Marines and is making his first combat jump onto a planet. No fighting between the main factions happens in our solar system or Alpha Centauri due to the fact that the Earth was almost destroyed. Humans have colonies on planets throughout the galaxy, and are able to get to them by going through hyperspace lanes. There are two European factions with one of them being called the European Confederation or something similar, a North American faction, a South American Faction, and a Russian Indochina faction.
In a later book we are introduced to the North American's spy agency where (potential spoiler) Number Three is the Marine Commander.