Keep the fight outside.

That’s the mantra uttered repeatedly by numerous current and former U.S. Capitol security officials.

The concept is simple enough. It yields the layers of security which the public, Congressional staff, journalists and others must navigate to gain entry to the Capitol. There’s always a squadron of U.S. Capitol Police officers roaming the plaza, guarding the doors, inspecting bags, riding their bicycles and cruising the immediate neighborhood in marked police cars.

There are covert methods, too.

For a few moments on Monday at 2:39 pm, questions arose as to whether the USCP’s defenses successfully quarantined “the fight” to an “outside” venue.

An initial report suggested that the altercation between USCP officers and suspect Lawrence Dawson unfolded somewhere outside the Capitol Visitor Center (CVC). The CVC is a rabbit warren of rooms and passages where police screen visitors for Congressional tours. Tunnels and escalators link the CVC to the Capitol itself. Curved, subterranean entryways stretch from the CVC toward the Supreme Court and the Library of Congress’s Jefferson Building across the street.

Outside is where something bad might go down. No one is inspected for weapons, fertilizer, detonators, dirty bombs, Polonium 210 or pen bombs as they approach the Capitol.

Officials pitched the entire Capitol complex into lockdown mode Monday, ordering those indoors to “shelter in place.” But once the USCP secured the scene and tourists started to spill out of the CVC, it became clear the incident unfolded indoors, where officers screen everyone entering the facility.

The screening hall resembles airport TSA checkpoint. Four lanes. Vertical metal detectors. X-ray machines and conveyer belts. Hard plastic containers to deposit watches, phones and jewelry. Officers observe those entering, scanning for signs of trouble or prohibited items.

Police and sources say Dawson walked up to the magnetometers. The machine signaled something was amiss. That’s when Dawson went for what was later described as an Airsoft pellet pistol. It’s manufactured to look like a Beretta, with a distinctive, wide barrel.

USCP shot Dawson once he drew the pistol.

Remember what we said about contraband…

You simply cannot show up at the U.S. Capitol, reveal a weapon -- even if it’s not a conventional firearm and “just” a pellet gun – and expect any other outcome. The U.S. Capitol is an appetizing target to terrorists and those who just don’t like government or Congress.

For every action, there is a reaction.

But what about that whole “keep the fight outside” business?

Dawson is in bad shape. Minor injuries to a bystander. No one else hurt. Nerves frayed. Children bawling. Promises to never penetrate the Beltway again. Hyperventilating Congressional staff. Breathless reporters.

And yet the business of government – symbolic and otherwise –  continued. No direct threat. Nothing linked to Brussels or ISIS or al Qaida. Just a guy who portrayed himself as a “prophet of God” when the cops hauled him out of the House chamber last fall for making a ruckus.

At first blush, it might look like the fight permeated the Capitol’s robust defenses.

But truly, USCP kept the fight “outside.”

“It appears the screening process worked the way it is supposed to work,” said USCP Chief Matt Verderosa, on the job precisely one week before Monday’s pandemonium.

Think about it. No one pierced the Capitol’s security perimeter itself. The “fight” was far away from the building. And while USCP may have technically neutralized Dawson indoors, he was still outside the Capitol and never came close to that building or other key Congressional environs.

Some of that is thanks to well-trained, quick-acting USCP officers. Some of that is thanks to the design of the CVC itself.

Congressional officials concocted the CVC so the public entryway is about two football fields away from the Capitol itself. Sure, people still can walk right up to the House and Senate Office Buildings and a similar scenario may have gone down in the foyers of any of those structures. Same with someone who was at the Capitol on official business or had an appointment – but harbored bad intent. But the CVC was built in such a matter to keep the fight outside.

Congress christened the Capitol Visitor’s Center in late 2008. It cost more than $600 million and was years behind schedule. Talk about building a CVC dates back to the 1980s. Former Rep. Vic Fazio, D-Calif., chaired the House Appropriations Legislative Branch Subcommittee (the panel which funds Congress) in those days. Then-House Minority Whip Newt Gingrich, R-Ga.,helped torpedo efforts to build the CVC. At the time, Gingrich criticized lawmakers for wanting to spend money on themselves.

Gingrich came around to the CVC concept when he matriculated to the Speakership several years later. But Gingrich wanted private money to help bankroll the CVC.

The political dynamic of the CVC changed after Russell Weston Jr. shot and killed U.S. Capitol Police Officers Jacob Chestnut and John Gibson in July, 1998. Lawmakers dumped $100 million into the budget to launch construction. Plans to put together the CVC earned additional currency following 9/11.

In the spirit of orphaning the fight to “outside,” policymakers have discussed pushing back the Capitol’s security perimeter to the edges of campus. In other words, visitors (and for that matter, aides, official visitors, lobbyists and journalists) would clear security perhaps as far as a quarter mile from the Capitol itself. That would keep the internal campus secure – and certainly relegate the fight to the great outdoors.

But it doesn’t solve everything.

Former U.S. Capitol Police Chief and Senate Sergeant at Arms Terry Gainer advocated such an arrangement. But Monday night, Gainer was skeptical that a broader boundary would have quelled Monday’s chaos.

“Pushing back the perimeter for me would help more with suicide bombers than this,” said Gainer in a brief interview. “Wherever the perimeter is, that’s where the risk point is.”

Gainer says USCP would still have to engage the offender “somewhere.” Gainer echoed Verderosa.

“This was what the CVC was designed for,” said Gainer. “It worked. “

Moreover, Members of Congress loathe making the Capitol complex more inaccessible – or perceived to be inaccessible – by the public. USCP could lock the whole joint down. But then it wouldn’t be the people’s house. Not a good PR move everyone hates Congress to start with.

“It is a showstopper,” said Gainer about efforts expand the perimeter.

And so, there’s the Capitol Visitor Center. There’s a chokepoint just inside the doors of that facility – but far from the Capitol itself.

Gingrich initially argued that Congress shouldn’t spend money on itself. And to be clear, there was plenty to bray about with cost overruns and delays when assembling the CVC. But at the end of the day, the CVC is not really about Congress itself. It’s about the people. The three to five million people who line up outside the CVC to visit the Capitol, learn more about government and see how Congress works.

Periodically, U.S. Capitol Police officers bust someone coming into the CVC with brass knuckles. Some weed. Maybe a blackjack.

On Monday, they took down a suspect with a gun. Granted, it was a pellet gun. But who could tell at the time.

They wanted to keep the fight outside.

And they succeeded.