Often when I am bicycle touring, I carry 70 -80 lbs of carefully packed and balanced gear on my bike in panniers. Even with this little amount of weight the bike is more susceptible to fallover and handles like a slug....Any more weight then this, we switch our gear over to the bike trailer.

I have rode/walked my bike and trailer up some moderate, long and steep hills both on and offroad with these types of loads and let me tell you it is no fun even though I am in good shape, bike daily and log a few thousand miles a year. It is hard on the back, arms and the legs.

I could not imagine doing this with 100 - 200 lbs or more. I know I would be in rough condition if I had to do this continously for more then a day or two...

IIRC, the North Vietnamese had small "camps" set up every 10-15 klicks along the trail with very basic facilities prepositioned for travelers.