Subseries contains correspondence documenting Cooper's activities during the First World War, including training, combat, capture, and repatriation. Also includes letters from related veteran associations. Materials date from 1917 to 1973.

Subseries contains letters related to Cooper's service during the Russo-Polish War. Includes correspondence with family, as well as letter documenting his continuing involvement with associations and groups commemorating the conflict. Materials date from 1919 to 1980.

Subseries includes correspondence, certificates, and awards from the Polish military related to Cooper's service during the Russo-Polish War. Materials date from 1919 to 1966.

Contains correspondence, documents, publications, photographs, and memorabilia covering all aspects of Cooper's military career, including the Mexican border campaign, World War I, the American Relief Administration, the Russo-Polish War, World War II, post-retirement, and Cooper's own research materials on the Japanese attack on Pearl Harbor. Materials date from 1911 to 1977.

Contains photographs of Cooper on duty and on leave in France and upon return from German prisoner of war camp. Also includes an image of the 20th Aero Squadron. Materials date from 1917 to 1918.

Subseries contains correspondence, programs, photographs, and other materials related to a testimonial dinner held for Cooper on June 17, 1966. Materials date from 1966.

Contains correspondence, certificates, and photographs related to Cooper's work with the American Relief Administration. Materials date from 1919 to 1920.

Subseries contains reports, correspondence, personnel records, and photographs related to Cooper's service with the Fifth Air Force during the Second World War. Materials date from 1943 to 1964.

Contains correspondence, photographs, research, and other materials related to Cooper's post-retirement activities associated with the military. Materials date from 1911 to 1977.

Contains correspondence, research, photographs, and other material related to Cooper's service in the Russo-Polish War. Materials date from 1919 to 1980.