Speaking in his first interview with a U.S. news organization, Mr. Gülen spoke of watching news coverage of Monday’s deadly confrontation between Israeli commandos and Turkish aid group members as its flotilla approached Israel’s sea blockade of Gaza. “What I saw was not pretty,” he said. “It was ugly.”

Mr. Gülen said organizers’ failure to seek accord with Israel before attempting to deliver aid “is a sign of defying authority, and will not lead to fruitful matters.”…

Mr. Gülen preaches nonviolence, dialogue between Western and Muslim worlds, and an educational tradition that combines study of science and Islam. His newspaper columns, weekly Internet sermons and other messages have been collected into more than 60 books. His adherents number, by various estimates, three million to eight million…

Mr. Gülen’s detractors see him as a cult-like leader whose empire aims to train an Islamic elite who will one day rebuild the Turkish state. Soner Cagaptay, a Gülen critic who is a Turkey analyst at the Washington Institute for Near East Policy, estimates that 70% of the country’s police force are Gülenists—a counterbalance to Turkey’s powerful military, a secularist bastion.