Washington ? President Bush on Monday named close friend Tom Ridge to head the new Department of Homeland Security, but he said even the biggest government shake-up in more than a half-century can “neither predict nor prevent every conceivable attack.”

“We’re doing everything we can to protect America,” Bush said as he signed a bill creating the department. “In a free and open society, no department of government can completely guarantee our safety against ruthless killers who move and plot in shadows.”

With that sobering assessment from an East Room stage, Bush asked the Senate to confirm his nomination of Ridge and named two high-powered deputies: Navy Secretary Gordon England and Drug Enforcement Administration chief Asa Hutchinson.

A large portion of the department will take shape March 1, when the Secret Service, Immigration and Naturalization Service and a few other agencies transfer their employees and budgets to the new entity. The final pieces will be put in place Sept. 30, 2003 – more than two years after the attacks that prompted the overhaul.

Ridge, 57, is a Vietnam hero, a former congressman and longtime political ally of the Bush family who nearly 14 months ago left his position as Pennsylvania governor to serve in the White House. No one else was seriously considered for the job, Bush aides said.

As the president’s homeland security adviser, Ridge has won praise for improving communication between Washington and local governments. His most visible creation – the color-coded national warning system – became an instant butt of jokes but has helped Americans understand the ebbs and flows in terrorism threats, even if they’re still unsure what, if anything, to do about the dangers.

Bush initially opposed creation of a homeland security department. But, facing criticism from Democrats, he embraced the concept in June and used it as a political issue in the midterm election campaign.

“The continuing threat of terrorism, the threat of mass murder on our own soil, will be met with a unified, effective response,” Bush told an overflowing White House crowd.

He has given Ridge a daunting assignment to combine nearly two dozen agencies, $40 billion in budgets and 170,000 employees spread across a broad swath of federal bureaucracy and well-protected turf.

It is the biggest federal reorganization since the Defense Department’s birth in 1947, and critics warn that problems are sure to crop up.

White House press secretary Ari Fleischer said it could take more than a year to get the agency fully up and running. But the administration’s transition plan, devised in secret meetings near the White House for months, sets a more ambitious goal of next Sept. 30, officials said.

President George W. Bush launches the biggest government reorganization in more than 50 years, signing legislation that creates a new Department of Homeland Security. He also named current homeland security chief Tom Ridge to head the department Monday.

Agencies can begin moving to the new department 90 days after the plan is submitted to Congress, which Bush did on Monday.

The first wave of agencies folding into the department March 1 include the Secret Service, Coast Guard, Customs Service, Immigration and Naturalization Service, Transportation Security Administration, Federal Emergency Management Agency and the General Services Administration’s federal protective services.

The changes will continue in phases, according to a blueprint for the shift distributed by the White House on Monday night.

“I think it’s doable, but I wouldn’t expect all the warts to be worked out in the first year,” said Dwight Ink, a former Office of Management and Budget and General Services official.

The department will soon open temporary headquarters in the Washington area. Its long-term housing will be determined later.