The 4th Corps Observation Group is an inactive United States Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 unit. It was last assigned to the IV Corps

IV Corps (United States)

The IV Corps replaced the VI Corps in the Fifth United States Army's order of battle in Italy after Allied forces liberated Rome in the summer of 1944 when VI Corps was withdrawn to take part in Operation Dragoon, the Allied invasion of southern France. Initially the Corps had two divisions, U.S...

, United States Army Air Service

United States Army Air Service

The Air Service, United States Army was a forerunner of the United States Air Force during and after World War I. It was established as an independent but temporary wartime branch of the War Department by two executive orders of President Woodrow Wilson: on May 24, 1918, replacing the Aviation...

, during World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

 in France. The organization was inactivated in early 1919 as part of the United States withdrawal of forces from Europe after World War I and the demobilization afterwards.

Mission

The mission of the group was primarily to keep the friendly command informed of the general situation within the enemy lines by means of visual and photographic reconnaissances. It was called upon to effect, whenever necessary, the adjustment of U.S. artillery fire. In addition, it expected that the group would serve to complete the schooling of pilots and observers and render them more competent to undertake intensive operations elsewhere on a larger and more complete scale.

Components

• 8th Army Observation (Aero) Squadron
  8th Special Operations Squadron
  The 8th Special Operations Squadron is part of the 1st Special Operations Wing at Hurlburt Field, Florida. It operates CV-22 Osprey in support of special operations.-Mission:...
  
  , 31 Aug – 23 Oct 1918
• 90th Corps Observation (Aero) Squadron
  90th Fighter Squadron
  The 90th Fighter Squadron is part of the 3d Wing at Elmendorf Air Force Base, Alaska. It operates the F-22 Raptor aircraft conducting air superiority missions.-Mission:...
  
  , 1 Jul – 21 Sep 1918
• 135th Army Observation (Aero) Squadron
  22d Tactical Drone Squadron
  The 22d Tactical Drone Squadron is an inactive United States Air Force unit. It was last assigned to the 432d Tactical Drone Group, stationed at Davis-Monthan AFB, Arizona. It was inactivated on 1 Apr 1979.-World War I:...
  
  , Jul–Nov 1918
• 168th Army Observation (Aero) Squadron, 12 Oct – 31 Nov 1918
• 255th Army Observation (Aero) Squadron, undetermined

(designated for VII Corps)

• 278th Army Observation (Aero) Squadron, undetermined

(designated for VII Corps)

Engagements

• St Mihel Offensive, 12–16 Sep 1918

Aircraft

• AR-2 (Avion de Reconnaissance) (French)
• Airco DH-4B (British)