It is possible - I have even seen kits (for an M416, I think) that added a jeep style a frame to beef up the pintle area. I see UPS and US Mail trucks doing it often onthe interstate. Not being a solid connection between the 2 trailers, there would be alot of movement between them - especially at any speed. I think the military must have only done this in off road, tactical situations - when necessary. Not to mention if you had to back it up during your trip home! I could almost bet you that would be impossible!
A few years back my brother decided he had a need to pull a 10' trailer with his two 4 wheelers on it behind his 26' tag along camper (he had his golf cart in the bed of the truck). He said he had seen a few other campers pulling like that over the years, so he figured he'd try it. He mounted a reese style receiver hitch under the camper bumper (to the frame). and hooked the trailer up to the camper (unloaded). Them he went for a test drive. He started out in his neighborhood (small, fairly tight roads) and moved on up to the larger town roads, then out on the 2 lane highways. Everything went well until he got to the highway and got up around 50 mph - he could feel the small trailer swaying behind the camper, even though he couldn't see it. He didn't even try backing it up as there was no use. I guess the small movements of the long camper, by the time they got to the small trailer caused lots of movement in the small trailer. I f he could feel it behind the heavy camper, it must have been swaying wildly!
He removed the hitch and put a bumper mount one on it for a bike carrier. Just my little (sort of) personal experience in the situation - very dangerous, unless doing it off road, mounted correctly and VERY slowly.