U Thant was a Burmese diplomat and the third Secretary-General of the United Nations. He assumed the role following the death of Dag Hammarskjöld in a plane crash in the Congo in 1961, and soon became one of the most consequential players in international affairs for over a decade.

Thant's contributions to some of the key global challenges of the era were widely celebrated at the time but have since been overlooked—until now. A brilliant new biography, Peacemaker: U Thant and the Forgotten Quest for a Just World, places the former Secretary-General at the heart of several crucial moments of the 1960s, including the Cuban Missile Crisis, the Vietnam War, post-colonial struggles in the Congo, and much more.

The book is written by Thant Myint-U, a historian who has worked at the United Nations—and who also happens to be U Thant's grandson. In our conversation, Thant describes how his grandfather went from being a schoolteacher in rural Burma to, just 15 years later, playing a key role in mediating the Cuban Missile Crisis as UN Secretary-General. We also discuss Thant's efforts to end the Vietnam War before it escalated, and his work confronting a fascist regime in a breakaway region of the Congo. More broadly, we explore the lessons that the current UN system and its Secretary-General can draw from U Thant's remarkable tenure.

Thant Myint-U is the author of Peacemaker: U Thant and the Forgotten Quest for a Just World.