Encyclopedias, Almanacs, Transcripts, and Maps
- Arms Transfers
- Armstrong, James (Captain)
- Armstrong, James (Quarter-Master)
- Armstrong, John, Jr.
- Armstrong, John, Sr.
- Army Air Corps, U.S.
- Army Combat Branches: Armor
- Army Combat Branches: Artillery
- Army Combat Branches: Aviation
- Army Combat Branches: Cavalry
- Army Combat Branches: Infantry
- Army Culture
- Army Reserves and National Guard
- Arnauld Family
- Arno Allen Penzias
- Arnold's March to Quebec
- Arnold's Treason
- Arnold, “Hap” (Henry Harley)
- Aron, Raymond (1905–1983)
- Arsenals