April 15, 2015 5:46 PM EDT

Samantha Power first appeared in the TIME 100 in 2004, after writing a book that chronicled the most regrettable experience of my diplomatic career as U.S. ambassador to the U.N.—the failure to stop the Rwandan genocide. A brilliant journalist and human-rights advocate, she was rightfully hailed as the “new conscience of the U.S. foreign policy establishment.” But she was still in many ways an outsider, inexperienced in the realities of national-security decisionmaking.

More than 10 years later, Power is an insider, but she has retained her moral vision. As America’s U.N. ambassador, she has been a powerful friend to the displaced and downtrodden and a foe of dictators and despots. She has seen how hard it is to compel the world to act, but she has never stopped defending the values America holds dear. I once regarded Samantha Power as a critic. Now I am proud to call her a friend.

Albright is a former U.S. Secretary of State

Contact us at letters@time.com.

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