So former Chief of Department Joe Esposito has been appointed to head the city's Office of Emergency Management.

"He's been a legend for a long time in the NYPD," Mayor Bill de Blasio said when he announced Esposito's appointment last week.

Fair enough. Espo -- as he's known -- served as chief of department for 13 years, probably longer than anyone in NYPD history. He is the quintessential good soldier.

He was at Ground Zero the day the planes struck.

He put up with former NYPD Commissioner Ray Kelly for 10 years, testifying during the stop-and-frisk trial because Kelly did not appear himself.

Esposito was also considered the department's moderate voice. (Well, everything is relative.)

When Chief Thomas Galati of the Intelligence Division, on orders from his boss David Cohen, held up the arriving Iranian delegation to the United Nations for a weapons check at Kennedy Airport, infuriating the Port Authority Police, the Secret Service and the State Department's Diplomatic Security Service, officials of those agencies turned to Esposito to get Galati to back off.

Now he's taking over at OEM, which was founded to coordinate disaster responses. Started by Rudy Giuliani in 1996, its first headquarters, on the 23rd floor of 7 World Trade, collapsed on Sept. 11, 2001, shortly after the two planes struck the Twin Towers.

Who knows where it is now housed? (Answer: 165 Cadman Plaza East in Brooklyn.)

Who knows who its previous commissioner was? (Answer: Joe Bruno.) Or what he did?

Poor Bruno. Although he served for 12 years under Mayor Michael Bloomberg, he was shunted aside by Kelly, with the NYPD usurping the role of other first responders.

While Esposito may well be the most qualified person to head OEM in the city, he probably had some help from his Brooklyn constituency of Orthodox Jews, who have allies in the de Blasio administration.

Appointing Esposito to OEM does something else for de Blasio. Let's say Bratton leaves after a year or two. If de Blasio feels that Chief of Department Phil Banks -- believed by some to be Bratton's heir apparent -- is not quite ready for prime time, what better interim choice could de Blasio make than Joe Esposito?