Christy Mathewson, one of the greatest pitchers of all time, retired during the 1916 season at the age of 35.

He joined the war effort in 1918, serving in France as captain in the newly formed Chemical Warfare Service. - National Baseball Hall of Fame

Mathewson and Ty Cobb were never teammates, but they did serve together in the United States Army in France during World War I.

They were both also part of the first National Baseball Hall of Fame induction class in 1936.

- National Baseball Hall of Fame

This 1917 Ty Cobb model bat was used in games played by United States servicemen overseas during World War I. - National Baseball Hall of Fame

This medal was won by U.S. Army soldier and Major Leaguer William E. Marriott from Pratt, Kan., while playing American Expeditionary Forces baseball in Le Mans, France.

- National Baseball Hall of Fame

Eddie Grant played 10 Major League seasons (1905-15) with the Cleveland Naps, Philadelphia Phillies, Cincinnati Reds and New York Giants.

Grant, who retired after the 1915 season, enlisted in the Army immediately after the United States entered World War I. Not long after his enlistment, Captain Grant was sent to the front lines in France. - National Baseball Hall of Fame

On Oct. 5, 1918, Grant and his men marched to the valley where the famed "Lost Battalion" was stranded before German shelling stopped the advance. Grant was killed in the ensuing battle.

The New York Giants held a memorial service for their former player in 1919.

- National Baseball Hall of Fame

Grant was the only Major League player to die serving in World War I. His alma mater, Dean Academy, produced a eulogy book as a tribute. - National Baseball Hall of Fame