Support troops are not armed or trained or organized to be effective in combat.
Wrong, wrong, and wrong. They are armed. The training has changed in the Army to try to make every soldier a warrior (e.g. every Marine is a riflemen) and teach the basics of how to react to ambushes, etc.
Perhaps I should have been more specific. Of course support troops are armed. They have personal weapons, rifles, pistols, a few machine guns. That is not comparable to the weaponry available to combat arms units.
And, of course, they are trained to properly respond to situations they are likely to encounter. But knowing how to react to an ambush on a convoy is not the same thing as knowing how the quell a riot or clear a house or operate heavy weaponry.
There are vast differnces in the organization, training and weaponry of combat arms (armor, infantry, artillery, etc.) and the training and weaponry of a support units (supply, maintenance, transportation, etc.).
For example, a unit organized to take and hold ground (infantry) is organized with fire teams, rifle squads, heavy weapons squads, etc. A unit organized to process personnel requests is organzied far differently. Can a unit be re-organized? Sure, takes time and training. And, equipment. A personnel, transportation, or maintenance unit doesn’t even have the communications gear to function effectively as a rifle company.