More people of that era and region were familiar with the care and maintenance of horses than with the care of machinery, and it was easier to collect forage for horses from the surrounding region than to collect fuel for vehicles. Mechanized units - tanks, mechanized infantry - tended to rely on mechanized supply and artillery in order to keep pace with the tanks and half-tracks, but it wasn't uncommon for the slower units - foot infantry, artillery - to rely on the slower equine transport. (I differentiate here between a unit's indigenous artillery - typically smaller caliber pieces intended for use on the battlefield with the unit - and the larger artillery unit, which used the big-caliber guns and generally located itself well back from the fighting.)

"Robbins’s claim fails because the Hobbs Act does not apply when the National Government is the intended beneficiary of the allegedly extortionate acts."