Both vehicles must be able a 60 degree slope (going up and coming down). The vehicles must have a roll over bar (similar to one used on a successful Israeli military ATV.) Both vehicles must be able to convert to tracks for travel in snow or very marshy terrain. SOCOM expects to buy up to 700 of each vehicle.
These military ATVs are developing the same way the HYMMWV (hummer) came about. Engineers at the jeep division of American Motors (that eventually became AM General) had been brainstorming new ideas for an improved "jeep" class vehicles ever since World War II. The 1970s was also a time when the concept of cross country vehicles for the masses was taking hold. So when the army came to AM General with the HMMWV proposal, it was not a bolt out of the blue. Army officers and vehicle engineers had been discussing new vehicle ideas for decades. In that sense, the HMMWV was evolutionary, not revolutionary (although a lot of ideas finally found their way into a production vehicle only with the actual design of the hummer.)
The army didn't go to AM General with a detailed spec for the HMMWV, but asked AM (and the automotive industry in general) to come up with a new tactical vehicle that was more mobile, and could carry more stuff, than the current tactical vehicles (Jeep, 3/4 ton truck, Gamma-Goat and others.) The army issued an RFP (Request For Proposal) and got two competing designs. AM Generals effort won hands down. The RFP approach is pretty typical. The armed forces does not try to design stuff, and the specs in the RFP are often kept pretty loose in order to let the contractors to use their imaginations.
SOCOM (Special Operations Command) has been using dune buggies and other small off road vehicles for decades. But civilian use of these vehicles has been growing in the last decade, so SOCOM has decided to ask the manufacturers to come up with proposals for two militarized ATVs (All Terrain Vehicles). One would be a 4x4 vehicle with a 900 pound payload and not weigh more than 1,950 pounds. This would be used by Special Forces and commandoes in the field. Top speed must be 88 kilometers an hour on a flat surface (72 when carrying a full load.) Range on internal fuel (on a flat surface) must be 160 kilometers. This assumes an average mission of 3.7 hours, covering 51 kilometers. It is assumed that the ATV would spend, on average 10 percent on of its travel on good roads, 20 percent on secondary roads, 65 percent cross country and less than five percent in a shot up (and rubble strewn) urban area. SOCOM wants a multi-fuel engine (common in military vehicles these days.) The 6x6 vehicle must be able to haul 1200 pounds and not weigh more than 2,300 pounds. Range on internal fuel (on a flat surface) must be 80 kilometers.