Final answer:
The main difference between the M1120A4 and M1120A2 is that the M1120A4 is the newer version which includes updated safety systems, electrical improvements, upgraded armor, and better integration with modern technology, while the M1120A2 is the predecessor lacking these enhanced features.
Step-by-step explanation:
The M1120A4 and M1120A2 are both variants of the HEMTT (Heavy Expanded Mobility Tactical Truck), which is a series of eight-wheel drive, diesel-powered, tactical trucks used by the US military. The primary differences between the two models can be seen in technological and design updates.
The M1120A4 is the later model and features improvements such as enhanced safety systems, improved electrical systems, an upgraded underbody armor kit, higher capacity for integration of modern communication and computing equipment, and increased compliance with the Army's Long-Term Armor Strategy (LTAS). On the other hand, the M1120A2 is the earlier version and lacks some of the updated features and enhancements found in the A4 variant.
For example, while it may have provisions for armor, it does not have the same level of integration with advanced armor configurations or the electronic upgrade packages available on the A4.