Context : The President of the United States of America, authorized by Act of Congress, July 9, 1918, takes pride in presenting the Distinguished Service Cross (Posthumously) to Second Lieutenant (Air Service) Frank Luke, Jr., United States Army Air Service, for extraordinary heroism in action while serving with 27th Aero Squadron, 1st Pursuit Group, U.S. Army Air Service, A.E.F., near St. Mihiel, France, September 12 to 15, 1918. 
Subject : Frank Luke 
Relation : conflict
In which war/battle did Frank Luke fight?