Fans of baseball should be well acquainted with each story of Bob Feller, Hank Greenberg, Joe DiMaggio and Ted Williams.  They left the primes of their careers to serve in WWII.  The statistics that would have been compiled are mind numbing to think about.  All of these players lost out on 3+ seasons to support their country.  Here are their stats if interested: Bob Feller , Hank Greenberg, Joe DiMaggio and Ted Williams.  Ted Williams also participated in the Korean War as well.  A brief rundown of Ted Williams combat experience: commissioned officer and pilot in the United States Marine Corps, wingman for Senator John Glenn, shot down once, and awarded the air medal.  Imagine the totals he would have put up without missing 1942, 1943, 1944, 1945, 1952, and 1953...  Yeah thought about it, um, wow.

FDR did a great thing in allowing Major League Baseball to continue for the 1942-1945 seasons.  The game was essential to the morale of the country at the time.  I only named the most famous of the ball players who contributed to the war effort, but there were many baseball players who gave up their playing careers to help their country.  Lesser know major leaguers lost their lives and gave the ultimate sacrifice to their country.  Elmer Gedeon and Harry O'Neill lost their lives during WWII.

The Cincinnati Reds own Eddie Grant died in the Meuse-Argonne Offensive in 1918 in The Great War.  He was a lawyer, a graduate of Harvard, a pro baseball player, and a Captain in an Infantry Division. 

Ty Cobb, Christy Mathewson, and a slew of other players contributed stateside to the efforts of The Great War.  Players were combat veterans of the Civil War, Spanish American War, WWI, WWII, and Korea.  Many MLBers also participated on weekends in the National Guard in support of the Vietnam War.  I can't think of or find anyone in the Gulf War, Operation Enduring Freedom, or Operation Iraqi Freedom.