Complex sentence: He was elected captain of next year's team at season's end, but instead served in the U.S. Army during World War I as a lieutenant in 1917 and 1918, then returned to Vanderbilt for his senior year in 1919.
Split into simpler sentences: He was elected captain of next year's team at season's end, but instead served in the U.S. Army during World War I as a lieutenant in 1917 and 1918. Cody then returned to Vanderbilt for his senior year in 1919.