When the United States entered World War I in April 1917, baseball had been America's national past time for about 60 years. The start of the war also coincided with the start of the 1917 MLB season. Many professional ballplayers would serve in the military, forcing MLB's response to the war to evolve over the 1917-1919 seasons. At the same time, American troops in Europe created hundreds of baseball diamonds and played thousands of baseball games during the war and the occupation that followed. To discuss baseball and World War I, we recently sat down with Al Barnes, co-author of the book Play Ball!: Doughboys and Baseball during the Great War.