Fixed nitrogen was in short supply at the beginning of the 20^th century. This shortage was the driving force for research to develop an industrial process to convert elemental nitrogen to combined forms of the element. The search for such a process had been ongoing for over 100 years. The story of the physical chemistry research by Fritz Haber in the first decade of the 20^th century will be discussed and the scale up of these developments by Carl Bosch will also be described. Haber received the Nobel prize in Chemistry for his work in 1919 and Carl Bosch in 1931 for the development of chemical high pressure methods that led to industrializing the process. The benefits of the Haber Bosch process to food production and the welfare of mankind will be discussed. More recent challenges to the environment due to plentiful fixed nitrogen will also be discussed.