​The courage of Muhammad Ali

Former Cleveland Browns Hall of Fame running back Jim Brown presides over a meeting of top African-American athletes who supported boxer Muhammad Ali's refusal to fight in Vietnam on June 4, 1967. Pictured: (front row) Bill Russell, Muhammad Ali, Jim Brown, Lew Alcindor; (back row) Carl Stokes, Walter Beach, Bobby Mitchell, Sid Williams, Curtis McClinton, Willie Davis, Jim Shorter, and John Wooten.

Tony Tomsic/AP

Muhammad Ali first achieved fame as a fighter in the ring. He went on to show his mettle as a fighter in the wider world. CBS News Special Correspondent James Brown explains:

As the world mourns the passing of Muhammad Ali, I can't help but think of all of the athletes I have spoken with over the years, who simply revere the man known as The Greatest.

Before Ali became an international icon, he was first and foremost a sportsman -- a heavyweight boxer who possessed incomparable speed, agility, and with a mouth to match.

He bragged about what he could do in the ring, but it was his willingness to speak truth to power that made him so influential to generations of athletes who followed him.

By coincidence, Ali died on the eve of the 49th anniversary of what has become known as the "Ali Summit."

On June 4, 1967, Ali was a 25-year-old champion who had shocked the world by beating the likes of Sonny Liston and Floyd Patterson ... but he also shocked America when he opted out of the draft for the Vietnam War because of his religious convictions as a Muslim. Ali immediately was reviled for his stance.

In an effort to find out whether the young boxer was sincere, another "great," Jim Brown, organized a meeting in Cleveland with Ali and several prominent athletes. Among them were Bill Russell and a 20-year-old Lew Alcindor, who later would change his name to Kareem Abdul-Jabbar.

Many of these athletes had served in the military and thought they could change Ali's mind. But after several hours of debate, the young champion actually changed their minds.

NFL Hall of Famer Bobby Mitchell was there, and said of Ali: "He convinced us that he knew exactly what he was doing, that it was important to him."

So the group held a press conference and came out in support of Muhammad Ali ... and the picture is truly worth a thousand words; sitting next to some of the greatest athletes of all time is the man who would eventually be known as the greatest of them all.

He would still be stripped of his title later that year and have to wait another three years to fight again. But that press conference began to turn the tide of public opinion for the man who would become a transformational figure in the world of sports.

He convinced them back then. And he convinced us all that to be great means to be courageous.

As he once said, "Impossible is just a big word thrown around by small men who find it easier to live in the world they've been given, than to explore the power they have to change it."