He was the son of a wealthy banker in Eastern Europe, a bohemian who liked to go out to nightclubs and yet became a pivotal figure in the twentieth century; before the onset of the Second World War, he was an outstanding mathematician and physicist, the youngest among the first five tenured professors hired by the Institute for Advanced Study at Princeton (he was 29 at the time, while the eldest of them, none other than Albert Einstein, was 54). During the Second World War, he proved indispensable to the Allied forces, including the Army, the Navy, the United States, and the United Kingdom, because he was the foremost expert in explosion theory and the designer and promoter of the first atomic bomb. After the war, the field of game theory, which he founded, greatly expanded the research of mathematical economics and influenced the work of at least 11 Nobel Prize in Economics recipients. His greatest contributions may have been in the theory and practice of computer science, and he is considered a founding father of the electronic computer. In short, he was the most useful talent to come from abroad to the United States in the twentieth century. This is the subject of this chapter, none other than John von Neumann, who was born in Hungary into a Jewish family not long after the turn of the century.