Battlefield U.S.A.

Again, the horror. Again. And again. And again, now with barely a breath between bouts of slaughter by gun barrel, in a blood-soaked nightmare from which this nation will not wake — unless and until it gains the collective guts to confront those who peddle and promote weapons of death. Fill in the dateline: San Bernardino, Calif. Fill in the scene: a holiday party for local public-health officials in a center for the developmentally disabled.

Fill in the perpetrators: up to three, armed with assault rifles and handguns.

Fill in the motives: still unknown as of this writing but inconsequential, inasmuch as it takes nothing but a fit of pique for the deranged or determined killer to pull a trigger again and again.

Fill in the lives lost: at least 14 innocents with the misfortune to live in a nation gone gun crazy.

And crazier, and crazier — a nation now populated with more firearms than people, where the 355 mass shootings so far this year exceed the number of days elapsed.

They encompass the carnage inflicted by deranged shooters in Colorado Springs, Charleston and Roseburg. Count among them scores lost, children not spared, in domestic violence.

Do not forget the jihadist slaughter of four Marine recruiters and a Navy sailor in Chattanooga.

All coincide with a chilling upsurge in firearms sales this year, as measured by background checks conducted by the FBI. If this year’s pace persists, 2015 will set a record for legal gun buying, capped by an astonishing 185,345 purchase requests on Black Friday alone.

Buying now routinely surges after gun atrocities. People may think they’re protecting themselves. But the number of lives snuffed out by gun violence dwarfs those saved by hero bystanders.

In San Bernardino, the killers wore masks and tactical gear and were armed to the teeth. This is the stuff of war, waged on Americans here at home. And members of Congress — let’s be blunt, Republicans in Congress — are surrendering. They are saluting the flag of the National Rifle Association.

In thrall to this flag, lawmakers fail to even permit discussion of a bill to subject suspected terrorists to background checks for firearms purchases.

In thrall to this flag, they let guns enter the hands of the mentally deranged.

In thrall to this flag, they resist universal background checks supported by nine out of 10 Americans — and by most gun buyers. And refuse to ban assault rifles. Or limit high-capacity magazines.

As long as they remain in thrall to this flag, ever more Americans will arm themselves, and ever more Americans will die.