The GMC CCKW

The big test for an MV is when the commanders request a night time motor march (convoy to you dudes) with trailers attached, to evaluate the unit's capability.
It will be conducted under BO conditions, just the BOD and BO Markers.
It weeds out the bugs quite fast.
Rarely will all vehicles have 100% functioning lights. It is an embarrassing time for Company Commanders, Motor Officers, and the Motor Sergeant, as they are scored for the performance of their vehicles. Ysually it is a driver that has not coupled the trailer correctly or learned how to use the Light Switch.

I remember the time when US Forces were stationed in my hometown in Germany up to the late 80's.
When they went out with their vehicles for a motor march the complete route was littered with broken down trucks, tanks etc. from beginning to end. Must have been embarrasing for these GIs watching us civilians passing by grinning and waving hands.

The Army was short on Ordnance manpower in Europe in the late 80s, many National Guarfd Support Units volunteered their Annual training to go to Europe to assist. It wasn't enough.