What a difference a decade or so can make: In 1993, Bernard Kerik was an undercover narcotics detective volunteering on the New York mayoral campaign of a former U.S. attorney, Rudolph Giuliani. Last week, President Bush announced he wanted Mr. Kerik in his cabinet as the director of homeland security.

This trajectory is more than a matter of being in the wrong place at the right time. America came to know Bernard Kerik when he served as New York City police commissioner during the attacks of September 11, 2001. He seemed to appear out of central casting – tough, no-nonsense, all results and no excuses.

But behind the power-lifting Dragnet persona was a man who had climbed the ladder of the American Dream rung by rung with steely determination and ample street smarts. He was born in Newark, N.J., to an alcoholic mother who abandoned him and was believed to have been working as a prostitute when she was found dead in 1964. Mr. Kerik’s high school guidance counselor harshly recommended that he focus his efforts on something other than academics. But Mr. Kerik proved a quick study in real life, relentlessly applying the lessons taught by a teacher named Mr. Giuliani.

After a successful mayoral election, many people line up for plum positions such as commissioner of a city agency. Far fewer ask to be made assistant commissioner, and of these, even fewer ask to be assigned to the largely thankless Department of Corrections. But after serving in the military, tutoring Special Forces in karate, and working as a military policeman in Korea, Mr. Kerik had briefly worked as warden of the Passaic County jail. He understood the important interplay between criminals on the street and those briefly behind bars. More importantly, he clearly understood the mandate from Mr. Giuliani – reduce crime and restore order by imposing accountability.

As chaotic as New York City streets were in the early 1990s, conditions inside New York City jails were improbably worse. A 1994 New York Magazine cover story pointedly asked, “Is Rikers About to Explode?” First as deputy commissioner to Michael Jacobson and then as commissioner himself, Mr. Kerik was instrumental in bringing Mr. Giuliani’s CompStat system to the city’s 16 jails.

CompStat was a Giuliani administration innovation now used by police departments around the world. Standing for “Computerized Statistics,” the system broke down citywide crime data by precinct in close to real time, holding commanders accountable for deteriorations in their community’s quality of life and allowing for rapid deployment of resources. The consequent and historic decline in crime proved Mr. Giuliani’s managerial insight: “What gets measured gets done.” The supposedly “ungovernable city” quickly became not only governable, but the nation’s safest large city.

Mr. Kerik understood both the mayor’s expectations and the effectiveness of the program, so he set out to develop a CompStat program for the 12,400 employees and estimated 130,000 inmates in the city’s jails. It was dubbed T.E.A.M.S. – Tactical Efficiency Accountability Management System – and its effect was electric. The city had been averaging more than 1,000 “slashing and stabbing” incidents a year by prisoners inside jailhouse walls wielding weapons ranging from razor blades wrapped in electrical tape to toothbrushes sharpened into homemade knives. In one bloody two-month period during the summer of 1994, there were 176 stabbings on Rikers Island alone. By the end of the decade, with Mr. Kerik as commissioner, there were 102 citywide – marking a 90% decline even while the prison population had gone up considerably because of the war on crime. This was a success few experts had predicted.

As commissioner, Mr. Kerik also kept in mind the lessons he’d learned as a beat cop – namely the importance of different law enforcement agencies working together. His innovative Gang Intelligence Unit tracked gang members’ activities in prison, providing valuable information to federal and local authorities and helping to further reduce the crime rate.

In addition, Mr. Kerik’s strong management style enabled him to cut the number of sick days taken by corrections officers to 14 from an average of 21 days a year. He increased the number of arrests for crimes committed in jail to more than 100 a month from an average of 10.

These successes over a period of five years were rewarded when Mr. Giuliani named Mr. Kerik to serve as police commissioner in August of 2000 for the final 16 months of the term. Mr. Kerik proved both effective and popular, reducing crime an additional 12.5%. He also won praise for improving police community relations.

Of course, it was his steadfast leadership of the NYPD in the aftermath of the September 11 attacks that solidified his reputation in New York City and across the nation.

New York City’s former top cop will now be the nation’s top cop in the all-important area of homeland security. His firsthand experience on the front line in America’s war on terror will serve him and the nation well. He brings a beat cop and seasoned investigator’s insights into an unwieldy 180,000-person agency with 22 divisions. As a respected Giuliani administration alumnus, he understands how to implement the hard-charging management strategies on a sometimes slow moving bureaucracy. He understands the unique challenges facing high-profile urban targets – something that will make our city and nation even safer while keeping terrorists on the run.

Mr. Kerik is a potent local addition to a Cabinet that seems dedicated to proving that the American Dream is alive and well. Now armed with New York street smarts, Mr. Kerik’s Homeland Security Department will play intense offense as well as defense, and help us ultimately win the war on terror.