A lot of Military Trucks have Diesel powered Inline-6 Engines that have a Turbo.
Inline-6 = 6 Cylinders in a straight line. Like this say this is the Engine block without the valve covers. [OOOOOO] All the Os are cylinders where the pistons that drive the Driveshaft are. A V8 would have a layout like the one below
[OOOO] four on this side ---------- typically a 90 degree angle (to give it the distinctive V shape) [OOOO] four on this side
A V6 would look like this [OOO] -------- [OOO]
And a Turbocharger is a method of Forced Induction that sends extra air into the Cylinders to combine with the Fuel (in this case Diesel) to create Combustion. The more Air (aka the bigger or stronger the turbo/supercharger is) that goes into the Cylinders the more it can combine with Fuel to create Horsepower.
A Turbocharger uses already expended exhaust from the engine to feed right back into the Engine where it spins it and blows compressed air into the Cylinders.
A Supercharger on the other hand uses a pulley fed by the engine to turn it's parts on the insides at high speeds which compresses the air and sends it into the Cylinders.
So by me saying you probably use an Twin Turbocharged Inline-6 Cylinder Engine you would have the 6 Cylinders lined up with an intake from both Turbochargers into the Cylinders which creates large amounts of Horsepower and Torque without only getting say 4 miles to the gallon, because you're using more Air rather than just using raw Diesel with just enough air to make a combustion.
A truck like these don't need a lot of horsepower, so your trucks would be tuned to have higher Torque than Horsepower. Because if we compare it to a runner running track. Lets say the runner can move his legs extremely fast without his legs on the ground but when he touches the ground he's slow. That's because he has raw horsepower which is the ability to go fast. However lets say that there's another runner who has huge muscular legs that move slow in the air but he can move himself quickly because he has the raw torque to move himself forward. That's because Torque is rotational force requiring to rotate the various gears and the powertrain to move the wheels (legs in his case). And there's one more runner who has a balance of both he has say a 50/50 split between horsepower and torque. He can move his legs fast, and he can also power his weight over the ground. He's the clear winner but if he were a car he wouldn't be able to pull as much weight as the guy with the muscle legs.