Not likely. The M983 HEMTT Tractor is only used as part of the Patriot system as its prime mover. Also, the M870 trailer is used by engineer units to haul construction type equipment, not combat vehicles. I don't think the M870 and M110 were in service at the same time either. The M110 was replaced by the MLRS in the mid to late '80s. Some National Guard units and the USMC still had them into the early '90s though.
It also depends on from what era you are talking about. For the Vietnam timeframe, it would have been an M123A1C tractor with M15A2 trailer. This combo was used up into the early '70s.
A more likely combo is the C-HET M911/M747 tractor-trailer combo mentioned by CapMac82 in your other post by the same name. This was used from the early '70s until replaced by the current M1070 HETS in the mid to late '80s.
Another option is a commercial tractor-trailer heavy transport combo if it is Operation Desert Storm (ODS, '90-'91) timeframe. The US military had a severe shortage of organic transport assets and hired out a bunch of Saudi commercial trucks to haul our equipment.
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