“martial law will be declared and roads blockaded with checkpoints. “
That would be a lot of troops. Where do those troops come from?
If things get that bad, current troops will be more concerned with the safety of their own families. Expect a number of desertions. For Reserves and National Guard, quite a few may decline to show up, it it means firing on friends and relatives.
One tactic would be to recruit "urban underclass" males, give them brief training, issue them Army uniforms and weapons, and have them man the checkpoints. After a few atrocities committed by "urban youth" masquerading as military, things will get truly ugly.
We don't know for sure, but they're likely to be wearing blue helmets.
Blue helmets make fine targets.
Where do the troops come from? Homeland Security....