Typically, they were (I guess still are) used by assorted command posts, medical aid stations and such in track laying outfits like Armor, Mechanized Infantry, Field Artillery and some Combat Engineers.
They had a gas engine driven 4.2 kW 28 Volt generator in the basket above the engine. It has a take-down davit and block and tackle to get the gen set off when you're going to be static for a while. The gen set lets you use all your commo gear without having to run the main engine.
There is a "tube tent" called an "Extension,Tracked Vehicle" by the Army that extends out from the rear of the vehicle. It makes a pretty spacious combo if you're going to set up for a while.
I spent 14 or 15 years of my career in the mortar business (right through MSG) I wonder how many thousand hours I spent in and around them?