On Jan. 24, 2003, Ridge took charge of about 180,000 people shuffled from disparate agencies that had existed elsewhere in the federal government before the 9/11 terror attacks prompted the creation of the new department.

Sen. Joseph Lieberman, the Connecticut Democrat, one of the original proponents of the department, said at the time, "It's like asking Noah to build the ark after the rain has started to fall."

Moving customs, immigration, border-control and other units under a new umbrella amounted to the most significant government reorganization in more than a half-century, since the Department of Defense was created just after World War II.

Yet the test of whether Ridge did a good job is said to be deceptively simple: Have terrorists struck again?

"We have to make literally hundreds of thousands, if not millions, of decisions every year," he said, "and the terrorists only have to be right once."

Ridge appeared to falter early in his Homeland Security duties, especially when thrust into the role of the president's spokesman on the anthrax outbreaks that began in the days before the creation of the department.

Later, his color-coding system to designate levels of perceived terrorist threats, and suggestions for households to stock duct tape, were often lampooned.

But Ridge grew into the job. In general, his standard of leadership was high, but he ran up against federal agencies whose bureaucracies remained more or less impervious to his influence.

Ridge's reported replacement, Kerik, won a lot of gratitude from New Yorkers in his handling of the 9/11 crisis. It's not clear, however, whether he is the superb and energetic administrator required to master his sprawling department.

Other challenges remain. The nation's chemical and nuclear plants, ports and even parts of the fortified aviation sector remain vulnerable to attack.

Today marks the 20th anniversary of the world's largest chemical accident, a tragic release from a plant in Bhopal, India, that has claimed over 10,000 lives.

Also this week, oil and chemical companies, through pressure reportedly applied by the White House, succeeded in fending off new chemical plant protections, despite heightened fears of terrorism and confirmed site vulnerabilities.

And the new secretary must tackle these crucial security issues without trampling on the rights of citizens.