Well, it will be between two factions, the United Nations Special Task Force (UNSTF) and a group of basic Soldiers from any country that can either be in training or already battle hardened. The whole army won't be there, just a few soldiers since I doubt several hundred roleplayers will join this.
The War will be over a virus held in a lab in Russia. (the exact location is still in the works since I don't know anything about Russia really, so the country might change) The virus has already been exposed to some cities, and both factions must wipe out the any living thing in each city before they can progress to the next and finally get to the actual Virus lab, since it is a duty to protect the rest of the world.
Both factions will also be trying to kill eachother while they're both in the same city, any weapons are available, as well as traits/skills as well as any equipment. Once a faction has gotten hold of the virus, they may continue to do as they wish with it, the result may or may not resolve in another chapter of the roleplay.
If you can't tell, this roleplay is still in the brainstorming stage, so if anyone has any suggestions just fire away.