The capital of the United States struggled to get back on its feet today, a day after a hijacked plane slammed into the Pentagon as part of the coordinated attack. President Bush, who returned to Washington last night, said federal agencies that were shut after the attacks on the Pentagon and New York’s World Trade Center will reopen for business today amid extraordinary security measures in the capital. Local fire authorities said up to 800 people are believed to have died when an American Airlines jetliner, commandeered at Washington Dulles International Airport, crashed into a newly renovated section of the massive Pentagon. Officials said the Pentagon would reopen today despite significant damage, with some personnel moved into alternate work sites. More than 20,000 civilians and military men and women work in the Pentagon, the world’s biggest office building and home to the Defense Department. District of Columbia Mayor Anthony Williams declared a state of emergency in the city, and all the hospitals in the region were put on maximum alert. Most of the federal government shut down yesterday. National Guard military vehicles blocked some streets near the White House and heavily armed police and Secret Service agents surrounded the gate leading into the Naval Observatory, the vice-presidential residence, as well as the British embassy. Military vehicles were seen rumbling through the city’s streets. The attack forced the evacuation of the White House and the U.S. Capitol and drove top U.S. government officials, congressional leaders and Supreme Court justices into safe but secret locations. The White House reopened later in the day.