During World War I Leach commanded the 151st Field Artillery Regiment, 42nd Infantry Division, and took part in the battles at Champagne-Marne, Aisne-Marne, St. Mihiel, and Meuse-Argonne.
During World War I, Leach commanded the 151st Field Artillery Regiment and 42nd Infantry Division. He took part in battles at Champagne-Marne, Aisne-Marne, St. Mihiel, and Meuse-Argonne.