1st Army (Italy)
1st Guards Tank Army
1st Cavalry Army
1st Army (France)
1st Air Army
1st Army Corps
1st Panzer Army
1st Red Banner Army
1st Parachute Army (Wehrmacht)
1st Army (Wehrmacht)
1st Guards Army (Soviet Union)
1st Army Aviation Brigade (Greece)
1st Army (Russian Empire)
1st Army Aviation Support Regiment "Idra"
1st Army (Kingdom of Yugoslavia)
1st Army Brigade
First Army
1st Army Corps (Armed Forces of South Russia)
1st Army Aviation Regiment "Antares"
1st Army Group (Kingdom of Yugoslavia)
1st Army Corps (France)
72nd Group Army
First Canadian Army
1st Guards Army
First Army (Romania)
1st Czechoslovak Army Corps in the Soviet Union
1st Army (Czechoslovakia)
1st Army of the West
First Army (Bulgaria)
First Polish Army (1944–1945)
1st Army Group Royal Artillery
First Allied Airborne Army
1st Army Tank Brigade (United Kingdom)
1st Army Tank Brigade
1st (Risalpur) Cavalry Brigade
1st Ukrainian Soviet Army
First Australian Army
1st Army (Austria-Hungary)
First Army (Japan)
1st Fighter Brigade
1st Corps (Army of the Republic of Bosnia and Herzegovina)
1st Shock Army
1st Manchurian Army
New 1st Army
Sapper army
1st Artillery Brigade (United Kingdom)
1st Military Region (Vietnam People's Army)
1st Tank Division (Imperial Japanese Army)
1st New Zealand Army Tank Brigade
1st Army Division (Argentina)
1st Special Forces Command (Airborne)
First Army (United Kingdom)
1st Division (Colombia)
1st Corps (Vietnam)
1st Heavy Artillery Regiment (Italy)
1st Infantry Division (United States)
1st Infantry Division (Romania)
1st Army Corps (Soviet Union)
1st Siberian Army Corps
United States Army Special Operations Command
1st Army Division (Peru)
1st Army (RSFSR)
51st Guards Combined Arms Army
United States Army Infantry School
First Western Army
1st Raider–Paratrooper Brigade (Greece)
Army Commissar of 1st rank
1st Royal New South Wales Lancers
First Russian National Army
1st Army (German Empire)
1st Division (Imperial Japanese Army)
1st Devonshire Engineers
1st Army Corps (Armenia)
Army Recruit Training Centre
First Army (United States)
1st Caucasus Army Corps
1st Cavalry Brigade (Imperial Japanese Army)
I Army Corps (Wehrmacht)
Tower Hamlets Engineers
1st Army (Yugoslav Partisans)
1st Army Corps (Russian Empire)
George Jeffreys, 1st Baron Jeffreys (British Army officer)
1st Hampshire Engineers
First Czechoslovak Army in Slovakia
1st Army Corps (Ukraine)
1st Independent Mixed Brigade (Imperial Japanese Army)
Alexander Hood, 1st Viscount Bridport (British Army officer)
Monument to the 1st Cavalry Army
Sir Donald Stewart, 1st Baronet
4th Cavalry Division (India)
Sir Edward Ward, 1st Baronet, of Wilbraham Place
1st Guards Division (Imperial Japanese Army)
First Army (Hungary)
1st Army Corps (Azerbaijan)
Para Commando Brigade (Bangladesh)
1st Fighter Air Defense Army
1st Lancashire Engineers
Far Eastern Front
Delta Force
600th Infantry Division
Dundee Fortress Royal Engineers
Cavalry Corps (Ireland)
First Army (Serbia)
Sir John Hamilton, 1st Baronet, of Woodbrook
Iraqi Ground Forces
First General Army (Japan)
Special Forces Regiment (Philippines)
Sussex Fortress Royal Engineers
Sir James Campbell, 1st Baronet
Sir Harry Smith, 1st Baronet
Sir William Houston, 1st Baronet
List of Australian Army medical units in World War I
1st Devonshire Artillery Volunteers
Bedfordshire Yeomanry
1st Construction Company (U.S. Army Air Service)
North Midland Divisional Engineers
West Somerset Yeomanry
1st Battalion, 168th Field Artillery (Nebraska Army National Guard)
First United States Army Group
Russian People's Liberation Army
Sir William Robertson, 1st Baronet
25th Infantry Division (United States)
I Royal Bavarian Corps
Lancashire Hussars
7th Operations Group
British Army First World War reserve brigades
City of Edinburgh (Fortress) Royal Engineers
4th Cavalry (India)
2nd Infantry Division (United States)
Glamorgan Fortress Royal Engineers
First Corps, Army of Northern Virginia
Robert Napier
New Zealand Expeditionary Force
New Zealand Intelligence Corps
Polish Armed Forces in the West
3rd U.S. Infantry Regiment (The Old Guard)
Sussex Yeomanry
Hampshire Yeomanry
3rd Operations Group
Austrian Armed Forces
Kent Fortress Royal Engineers
1st Guards Infantry Brigade (Imperial Japanese Army)
John F. Kennedy Special Warfare Center and School
1st Special Purpose Air and Missile Defense Army
Ninth Air Force
East Lancashire Royal Engineers
First Motion Picture Unit
Russian separatist forces in Ukraine
15th Fighter Aviation Division
Frederick Maurice (military historian)
15th (Imperial Service) Cavalry Brigade
Hollymoor Hospital
Units of the Royal Engineers
Royal Canadian Air Cadets