MacMillan is a history professor at the University of Oxford and was also Provost of Trinity College. For her work on this book, she had access to many private collections, including those of her great-grandfather, Prime Minister Lloyd George.
Peacemakers recounts in precise detail the six months of negotiations that took place in Paris, France following World War I. The book focuses on the "Big Three", photographed together on its cover (left to right): Prime Minister Lloyd George of the United Kingdom, Premier Georges Clemenceau of France, and President Woodrow Wilson of the United States. Other participants included Vittorio Orlando, premier of Italy; an Arab delegation headed by Faisal ibn Husayn (later King Faisal I of Iraq), T. E. Lawrence, and Gertrude Bell, the "Uncrowned Queen of Iraq"; and Ho Chi Minh, then a kitchen helper at the Ritz Hotel who submitted a petition for an independent Vietnam.
The acclaimed book details the conditions imposed on Germany and how three men rewrote the map of the world. The book also details other parts of the peace conference, such as Yugoslavia, China, Romania, Poland, and other major events throughout the conference. It also attempts to debunk a much-quoted theory of John Maynard Keynes, who propagated the idea that the conditions imposed on Germany in the Treaty of Versailles led to the rise of Adolf Hitler.
The work has been an international best seller, especially in the United Kingdom and Canada.
Douglas Brinkley, director of the Eisenhower Center, said, "Without question, Margaret MacMillan's Paris 1919 is the most honest and engaging history ever written about those fateful months after World War I when the maps of Europe were redrawn."