The civilians could do that too. All of the factories that make those bombs, tanks, and planes aren't military facilities. The fuel that powers them isn't from military wells. The bullets they shoot flow from civilian assembly lines.
The civilians side wouldn't immediately need military hardware. There are fields full of mothballed jetliners that could be made flyable in days. Imagine several hundred Boeing 707, 727, 747s, and similar 1970's/1980's airliners loaded to capacity with tons of high explosives flown by remote control into bases. All of that would take place while the weapons factories spun up to full capacity making the latest and greatest weapons on earth for the civilian forces.
The 300 million who wouldn't fight don't have to. They just have to do all the things the make our economy hum as they do now. In that scenario, it is the military that would be like trapped rats with no more food coming in, no more arms coming in, no more fuel coming in, no water coming in, all of the power lines cut, and completely surrounded as their adversaries got stronger by the minute.