My personal understanding. The field service, and the army's usual service is completely different. In the field, the troops left the base, the logistics system has to "start from scratch", tents and barracks, food and cooking, health care, equipment, fuel and ammunition protection, equipment maintenance, etc. These must have, and these equipment and the base of a lot of different, can be quickly deployed in the field, deployed, but also to be able to quickly transfer. And in last year's National Day parade to show a variety of field equipment, field refueling vehicles, medical ambulance cabin, field cooking equipment, and the details of the soldier's bath car, laundry car, of course, but also portable toilets and so on. And these equipment in the battlefield, but also to be able to withstand the test of the battlefield, such as resistance to enemy harassment, emergency mobilization, transfer, driving at night with lights closed, battlefield concealment and so on.
So the field service is a huge system, the need for perfect field defense equipment to ensure the normal training of our soldiers, to protect them to win the war.
I hope you will be satisfied with my layman's explanation.