In 1962, President John F. Kennedy delivered a speech that would become a defining moment of the 20th century.

"We choose to go to the moon in this decade and do the other things, not because they are easy but because they are hard," Kennedy said, speaking before an audience at Rice University in Texas.

Historian Nancy Koehn joined Boston Public Radio ahead of the 50th anniversary of the moon landing. She explained the leadership steps and qualities that made it possible for mankind to take that giant leap. Koehn is an historian at the Harvard Business School, where she holds the James E. Robison chair of business administration. Her latest book is "Forged in Crisis: The Power of Courageous Leadership in Turbulent Times."