Do empires build trade routes or do trade routes build empires? Have the United States and Russia been locked in an economic rivalry since the 1860s? Was World War I triggered by international grain trade and the desire of Russia to control Constantinople? “Oceans of Grain: How American Wheat Remade the World,” by Scott Reynolds Nelson, examines these questions and much more. It is a study of grain, its trade routes, and the impact grain trading has had throughout history. Bread is the staff of life. Nelson follows it from prehistory to the present. Nelson’s theme is simple: Food production drives history. Abundance or absence creates or destroys empires, fuels economic and technological growth, and drives world history. Grain is the most important food. Storable and transportable, it can also be used to create more food, especially meat. The two biggest breadbaskets are the Ukrainian and American plains. There were …