IN THE EARLY 1960S, a peaceful world seemed possible. The still young United Nations was regarded as humankind's best hope for ending war. African and Asian nations, having recently won their freedom from colonial rule, sought influence on the world stage. At the helm of their international efforts was Secretary-General U Thant, a practising Buddhist and former schoolteacher from Burma.

In Peacemaker, acclaimed historian Thant Myint-U traces his grandfather's integral yet forgotten roles in some of the twentieth century's most critical crises: from battling white supremacist mercenaries in the Congo and mediating an end to the Cuban Missile Crisis to desperately trying to prevent the 1967 Six Day War. Drawing on newly declassified documents, he traces U Thant's tireless efforts to bring peace to Vietnam, create a fairer international economy, safeguard the environment, and avoid a third world war.