Elmer Lindroth entered the US Army during World War I, having served before that as a lieutenant in the Illinois ational Gard. Lindroth fought in the Meuse-Argonne battle as a captain, where he led his company, a part of the 33rd Division in France. He remained in the Army after WWI, was promoted to major in 1919, lieutenant-colonel in 1940, and colonel in 1941. Lindroth earned degrees from the Commanding Officers Course, Infantry School in 1926, from the Command and General Staff School in 1927, and from the Army War College in 1934. For his services in the first World War, Lindroth received a Silver Star and a Purple Heart. He later served as senior aide-de-camp to Lt. General Hugh A. Drum, commanding general of the Eastern Defense Command.