The United Nations has been called everything from the best hope of mankind to irrelevant and obsolete. With this much-needed introduction to the UN, Jussi Hanhimäki engages the current debate over the organizations effectiveness as he provides a clear understanding of how it was originally conceived, how it has come to its present form, and how it must confront new challenges in a rapidly changing world.After a brief history of the United Nations and its predecessor, the League of Nations, the author examines the UNs successes and failures as a guardian of international peace and security, as a promoter of human rights, as a protector of international law, and as an engineer of socio-economic development. Hanhimäki stresses that the UNs greatest problem has been the impossibly wide gap between its ambitions and capabilities.