Members of the Secret Service are seen on the roof the White House September 29, 2014 in Washington, DC.BRENDAN SMIALOWSKI/AFP / Getty Images
The sharpshooters on the roof with their sniper scopes didn't kill the intruder racing toward the White House. The handlers on the North Lawn didn't unleash the powerful, unmuzzled dogs trained to take down any assailant. The armed agents, inside the grounds and outside among the tourist throngs on Pennsylvania Avenue, didn't shoot. The White House doors weren't locked. And the U.S. Secret Service agent inside the imposing main White House entrance was apparently so surprised when Omar J. Gonzalez burst in that he was able to just knock her aside.
No agent was stationed at the stairs leading to the first family's private quarters when Mr. Gonzalez ran past, deep inside one of the world's supposedly most secure buildings. Finally, an off-duty Secret Service officer tacked the intruder, who had a knife in his pocket, in the East Room.
Explanations and excuses are now pouring forth from Julia Pierson, who heads the $1.8-billion (U.S.), 6,700-person Secret Service which, despite other missions from tracking counterfeiters to guarding foreign dignitaries, has as its primary purpose protecting the president of the United States.
Critical to any postmortem of the incident is whether agents deliberately didn't kill Mr. Gonzalez because the White House security detail had reduced its threat-response level after Mr. Obama and his daughters had – minutes earlier – boarded one of the big white-and-green Marine helicopters and lifted off the South Lawn. Once the President and his close personal security detail, the highly trained agents supposedly willing to "take a bullet" if necessary to thwart an assassin's moves, are no longer present, the rules of engagement change.
"The President is safe," Ms. Pierson insisted.
Getting the hair-trigger response right goes both ways. Less than a year ago, Washington police chased and killed a disturbed young mother in a fusillade of gunfire after she rammed her car into bollards outside the White House and then fled at high speed. Her baby in the back seat escaped injury.
The bubble of presidential protection expands
When Abraham Lincoln headed to Ford's Theatre, he told his self-appointed personal bodyguard to take the evening off. The Washington police officer standing guard outside the presidential box slipped out to a local tavern. So no one was protecting the President when he was assassinated by a Confederate sympathizer in the theatre.
Each time an assassination occurs, or a plot is thwarted, the bubble of protection encasing the president gets bigger and thicker.
Bodyguards became a constant after Lincoln's assassination. But they didn't stop an anarchist from shooting President William McKinley in 1901, as he shook hands with citizens in Buffalo. The President died eight days later and U.S. Congress tasked the Secret Service, originally a federal agency created to track counterfeiters, with providing close personal security for presidents. By 1902, two agents were assigned full-time.
The service had grown massively by the early 1960s. But dozens of agents and a heavily armed motorcade failed to thwart Lee Harvey Oswald, who killed President John F. Kennedy from the sixth floor of the Texas Book Depository as he rode in an open limousine through Dallas in 1963.
Presidents from then on did not travel in open cars. Closed and bomb-proof limousines are now flown by military airlift so as to be available wherever the president travels.
After John Hinckley shot President Ronald Reagan in 1981 as he left the Washington Hilton, a special entrance was built to allow the president to move from a limousine into the hotel without giving an assassin firing lines. Other buildings have similarly protected access.
After a drunken pilot crashed his light plane into the White House in 1994, President Bill Clinton ordered a two-block stretch of Pennsylvania Avenue adjacent to the White House closed. After the Sept 11, 2001, terrorist attacks, heavy bollards were installed around an expanded White House perimeter to stop truck bombs.
In the past few days, a second fence, a few metres beyond the one scaled by the intruder at the centre of the latest security gaffe, has been erected. And the Secret Service director told a congressional committee that the front door to the White House now locks automatically in the event of a security breach.
The party crasher who laid hands on the President
The woman in red was a far graver security breach.
Far more serious than the fence-jumping, knife-carrying 42-year-old veteran who burst through the White House doors, knocked a U.S. Secret Service agent aside and ran deep into the mansion before being overpowered on Sept 19.
Far more dangerous than the barrage of gunfire – 29 shots in all – fired at the White House three years ago. At least seven shots struck the mansion.
In both cases, Mr. Obama wasn't in the White House. And while the the primary person the Secret Service must protect is the President, his children were inside, and the first lady reportedly ripped a strip off top Secret Service officials after learning from an usher that bullets had hit the house while her daughters were inside.
But the lady in red got within knifing distance of Mr. Obama.
Unvetted and unknown, she penetrated the White House and laid hands on the President.
She was much closer than John Wilkes Booth when he shot President Abraham Lincoln in the Ford Theatre. She was much closer than John Hinckley Jr., who shot Ronald Reagan as he exited the Washington Hilton in 1981.
Michaele Salahi, the gate-crashing, disgraced socialite, was so close that she was holding the President's hand, grinning as she chatted to Mr. Obama inside the White House after breaching both the building's perimeter security and the close personal detail of agents.
Ms. Salahi and her then-husband, Tareq, weren't invited to the hot-ticket 2009 state dinner in honour of India's Prime Minister, the Obamas' first such glittering event. Instead the aspiring wannabe guests sneaked in by hopping out of their car and getting in a line for dinner guests – past the cordons of security personnel that were supposed to vet the identities of the 1,836 invitees, past the weapons detectors and past the agents deployed to keep unwanted strangers out of the White House and potential assassins away from the President.