It is not a HEMMT. It is an M1074 PLS (Palletized Load System), based on the HEMMT truck, just longer and beefier. The back has a flat-rack that it can be off-loaded and another picked up to transfer supplies, artillery rounds, etc. It works simmilar to a large industrial dumpster that you see at construction sites that are loaded on and off a truck.
More info here:
http://www.fas.org/man/dod-101/sys/land/pls.htm
http://www.primeportal.net/hemtt/m1075_walk.htm
http://www.primeportal.net/hemtt/m1075_pics.htm
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