FORTUNE — Eleven years ago today, Salvatore Cassano was working as the chief of operations for New York City’s Fire Department. His leadership during one of the darkest days in the city’s history ultimately earned him the position of its 32nd commissioner, a post he has held since January 1, 2010.
Commissioner Cassano joined the FDNY in 1969. He says he never dreamed he’d make it to commissioner; he decided to become a firefighter based on a recommendation from his brother. Now at the highest spot in the department, Cassano is responsible for the lives of 10, 725 uniformed firefighters and officers as well as thousands of fire marshals, EMTs, paramedics, and other support personnel. On the 11th anniversary of the September 11 attacks, Commissioner Cassano shares what he’s learned about training and leading New York City’s finest.
An edited transcript is below.
Fortune: Why do you think you were appointed commissioner?
Salvatore Cassano: I think the biggest attribute that people saw was that when I came up through the ranks, I respected the people that I worked for, but equally, I respected the people that worked for me. I would never ask anybody to do anything that I wouldn’t do myself or hadn’t done myself. I know how dangerous a job it is to be a firefighter.
Most people don’t. What is it really like to go into a burning building?
It’s nothing like you’ve ever seen in a movie. Because if they really showed you the interior part of a fire, you wouldn’t see anything but black smoke. Now, we have improved masks that I never wore and they really protect firefighters. But it’s still very dangerous because with the gear, you can go in a little further than we went in the past. So if you have to get out, you’re going to have to travel further.
What I would describe is it’s pitch black, and it’s very hot and you’ve got to get down to the floor as low as you can where there’s maybe some air.
How does the department prepare its people for life-or-death situations like that?
The amount of training since September 11 has gone far and above any of the training that we had done in previous years, out of necessity. We lost 343 members of the department, and we had to increase training in light of all the different types of jobs we were going to be asked to do. We call ourselves an all-hazard department now because we don’t just respond to fire, we’re involved in terror prevention, hazmat, medical emergencies, non-medical emergencies. We respond to man-made natural disasters: hurricanes, tornadoes and earthquakes.
How do you, as a leader, keep your people dedicated after something as traumatic as the losses you suffered on September 11?
It was the most difficult period this department has ever faced, but we came back pretty quickly because of how close we are. We’re like family to each other. You spend so much time with your fellow firefighters, sometimes 24 hours at a clip. You become real close, and that did help us recover.
Also, the way we took care of our families; I think that sent out a very strong message to the members of the department that you’ve got to put your life on the line, but if something does happen to you, we’ll pick up and help your family and make sure that they are taken care of and watched over. We’re still doing that.
Is it difficult to get people to put their lives on the line?
Our hardest problem is keeping people back, because they are so aggressive, which is good for everybody that they’re responding to, but sometimes it’s not good for them. Firefighters are always seen as this kind of person who’s going to jump through flames and is going to rescue people. That sounds good in a movie, but you’ve got to be smart enough to know when to go in, when to go in with a different mindset, and when not to go in.
There are some situations where we have to tell people the risk is not worth the reward. So if an apartment is fully involved — I mean fire from floor to ceiling — there’s nobody in there that’s going to be alive. You have to weigh that.
It takes a committed person to want to become a firefighter. It’s not just a job — I know that sounds pretty corny, pretty hackneyed to say, “Oh it’s not a job, it’s a calling.” But really, it’s such a true statement for the firefighters and EMTs and paramedics. Because with what we’re asking them to do and some of the sights they encounter, they really have to love their jobs.
Do you still love it?
I do love my job. I come to work every day, and I feel blessed that I can finish my career in a department where I spent my entire life.
As for September 11, it was the darkest day in the department, but it was also our shining moment. If you’ve seen the film, we were going into those buildings when people were coming out. We did what we were supposed to do, and we rescued as many people as we could. Unfortunately, we paid a heavy toll. But what September 11 has done for me and a lot of other people is that it drives us every day. As I’m speaking to you, I’m sitting in a chair and right opposite me is a framed collage of the photos of the 343 members that we lost. Every day when I come into the office, that’s the first thing that I see. And that’s there for a reason, because it reminds me of what we’re here for.