Federal authorities have begun to seal off a security zone extending miles from the Capitol, where President-elect Barack Obama will be sworn in on Tuesday, drawing on disparate lessons gleaned from terrorist attacks in London and Mumbai, the Sept. 11 attack at the Pentagon and even annual Fourth of July celebrations on the Mall.
Though intelligence agencies have detected no credible threat to any inaugural event or to Mr. Obama, law enforcement agencies, operating from a network of centers, will command ground, air and waterborne forces numbering in excess of 20,000 police officers, National Guard troops and plainclothes agents from more than 50 agencies, according to security planners.
The security measures, enhanced by a White House announcement of emergency financing for public safety, are by far the most extensive and stringent for the swearing-in of a president — a task vastly complicated by a crowd that is expected to reach two million to four million people who will face successive rings of security, each more restrictive than the last before they get near inaugural events.
The security is especially tight in part because the event is the inauguration of the first African-American president.
“As an agency, we have to prepare at the highest level,” said Malcolm D. Wiley Sr., a spokesman for the Secret Service, which has the overall responsibility for inaugural security. “We understand this is a historic event, but it is also tied to the size of the crowd we expect and our security information.”
The 240,000 people with tickets to the swearing-in and the thousands of additional people with tickets to watch the parade are only a fraction of the numbers expected to walk or take buses or subways to the Mall. Most of those without tickets, if they see anything at all, will watch on 20 Jumbotrons that the authorities, fearing that even a small incident could provoke a stampede, hope will keep people in one place.
While the federal security officials have not projected their total cost for the inauguration, officials in the District of Columbia have said the city might spend nearly $50 million. State officials in Maryland and Virginia have estimated they might spend $12 million and $16 million respectively, and officials in each of the three jurisdictions have said they hope the federal government will help pay for their expenses.
The security plan covers not just the events on Jan. 20, but also the welcome concert for Mr. Obama on Jan. 18 at the Lincoln Memorial, which is expected to draw as many as half a million people, and nearly 100 official balls, concerts and receptions that will not end until the early morning hours of Jan. 21.
So far, analysis of intelligence has not yielded evidence of an overseas or domestic threat, said Joseph Persichini Jr., who is in charge of the F.B.I.’s Washington office. But, he said, the assessment changes daily.
“This is a global event,” Mr. Persichini said. “The intelligence community and our partners are very cognizant of it. Everybody feels the urgency. We continue to believe the threat is low, but no lead goes untouched.”
He said that the overall security plan was largely an expansion of emergency response plans that have been in effect since the 2001 terrorist attacks.
“We’re taking what we do every day and magnifying it,” Mr. Persichini said. “That’s a challenge.”
It has been known that Mr. Obama’s election had resulted in threats against him and intensified racist commentary on Web sites used by white supremacists. In response, Mr. Persichini said that agents in the F.B.I.’s 56 field offices had been asked to review old files and contact sources to anticipate potential trouble.
Less visibly, federal authorities will deploy 155 intelligence teams of plainclothes agents throughout the region including at Metro subway stations in the outer suburbs of Virginia and Maryland. Based on the knowledge that the London subway bombers in 2005 used outlying feeder stations as staging points, the agents will move through the crowds on foot looking for suspicious behavior.
Teams of intelligence analysts, evidence response technicians, bomb experts, cybersecurity specialists, hostage negotiators, emergency medical personnel and SWAT units will also be nearby and out of sight in off-site locations unless they are needed.
Public and private buildings will be closed to normal business near where Mr. Obama will be sworn in and along the parade route up Pennsylvania Avenue. No one will be permitted to enter a nearly two-square-mile area without a bag search and passing through a metal detector. Officials have warned people not to bring strollers, folding chairs, coolers and umbrellas.
With roads and five major bridges leading into the city closed for the inauguration, and vehicular traffic excluded from large parts of downtown, transit officials have warned riders of “crush conditions” and long waits for buses and subways.
Fighter jets will provide air cover and Coast Guard boats equipped with automatic weapons will patrol the Potomac River. Chemical, biological and radiological detectors, installed after the Sept. 11 hijackings, are already in place.
Businesses and hoteliers have been briefed to be watchful during the inaugural events, in part because the authorities want to increase security awareness after the Mumbai attackers last November singled out soft targets like hotels that were lightly secured.
Salvatore R. Lauro, chief of the United States Park Police, which has jurisdiction over the Mall, said that the authorities had experience screening large numbers of people moving in and out of the open space during events like the Fourth of July celebration, so his worries focus elsewhere.
“We worry about normal criminal activity, we worry about terrorism and we worry about medical issues,” Mr. Lauro said. “But what keeps me up at night is the weather. It could be very uncomfortable for everyone. We’re just hoping for a nice January day.”
This story, "", originally appeared in The New York Times.