What qualities does it take to lead?

Daniel, great question. I have three attributes that I believe are the qualities of great leaders.
1. Humility. Nothing distances a leader from his/her troops quicker than a leader who is cocky and narcissistic. We don't need that and subordinates, peers, and superiors alike see right though it.
2. Courage. This isn't a death-defying, reckless attitude. It's a trait that demonstrates meticulous thought as to how to attack a situation, regardless of the opposition - or how it may make you look.
3. Servanthood. Serving your troops is the best way for them to appreciate your leadership.

That's like asking what qualities it takes to find inner peace. Being a humble, courageous, servant as LTC Strickland lays out would certainly be a good place to start, but if you were also a suck-ass who was all about pleasing your boss and you put that primary concern into those other three buckets, you might be one of the worst leaders ever. Don't get me wrong, I'm a LTC in the US Army, and I believe in doing what you're told, but there's a difference. I think intent has a lot to do with it and that's really hard to measure. WHY are you serving? WHY are you leading the way you are? That will drive WHAT you do. I recommend reading Marcus Aurelius' "The Meditations." Hell, he was Caesar. He probably has some decent things to say about leadership. He talks a lot about being humble...so that's probably spot on. Other thoughts...to be a good leader you still have to be a good follower - do what you're told and don't go off on your own tangents because you've always wanted to do "this" when you were a leader...care about the profession - I mean REALLY care about it. Find something to believe in and let people know about it. It gets to the WHY you do what you do. I know why I serve and I am vocal about it. I'd say you have to inspire people. People didn't join to flip burgers...well, except maybe the cooks...seriously though. Who wants to do this kind of job and just hear drivell from their leaders? They want to believe in something, to be part of the winning team, to be told that they are the sexiest bunch of knuckle dragging man killers on the face of the planet. Inspire people. Be visible. Treat everyone like their life is meaningful. Realize that they are more important than you are. Realize that IF you are good enough, IF you are inspirational enough, IF you treat people like grown-ass men and women, that maybe, just maybe, you will impact their lives and the lessons you impart on them, will be imparted on others...and others...and others as those people take on leaderhip roles. In that way, a real leader will live forever, their legacy passed down from leader to leader until the Army ceases to be.

I would say a tenacity for success. Not for your success but for the success of your men. They will make you or brake you. You must lead by example and serve your men when needed. I used to think that the Leader made the difference in the success of the mission. I was only partially right. The leader makes the difference by enabling his soldiers to be successful. If your soldiers are not successful it may not be their fault. I learned a long time ago that soldiers are a direct reflection of their leadership.

.....and all that stuff they teach you in Ranger School. RLTW!