IV Corps Observation Group The IV Corps Observation Group was an Air Service , United States Army unit that fought on the Western Front during World War I . It was demobilized on 12 May 1919 . There is no modern United States Air Force unit that shares its lineage and history . History . First Army Air Service . The IV Corps Observation Group was formally organized on 1 July 1918 by the First Army Air Service at Ourches Aerodrome , France , although its first personnel were organized on 27 June . It was formed for the purpose of operations in the forthcoming American offensives of First Army . It ' s units consisted of a Headquarters Squadron , the 135th Aero Squadron , arriving at Ourches on 30 July . A second squadron , the 8th Aero Squadron was assigned to the group on 31 August . Both squadrons were assigned to the Group from the 1st Observation Group School at Amanty Airdrome . The first efforts of the Group were directed towards organization and preparation for combat operations in the coming St . Mihiel Offensive . To this end , the 8th and 135th were designated as Corps Observation Squadrons whose duty it would be to make artillery adjustments , to perform photographic missions of the Corps front , to make long distance reconnaissances together with Divisional work . On 11 September , the day before the attack , Group headquarters moved to Ménil - la - Tour along with First Army AS Headquarters and IV Corps HQ . Throughout the attack , direct telephone communications were maintained constantly with the flying squadrons at Ourches . The group flew day observation flights over the St . Mihiel Sailent throughout the initial defensive action , then crossing the line and performing reconnaissance patrols over enemy infantry , roads and railroads while the First Army infantry was advancing . It Flew observation missions over the enemy lines , taking photographic strip photos over the entire front . One of the main missions was to photograph the entire corps line front to a depth of 10 km inside enemy territory , about 600 square km . Second Army Air Service . Headquarters remained at Ménil - la - Tour until 10 October when it moved along with IV Corps HQ to Bocq along the Belgian - French border . On 12 October , the 168th Aero Squadron , located at Gengault Aerodrome , Toul , was assigned to the group . It was a newly organized unit and had just arrived at the front . On 14 October 1918 , the Group was relieved from First Army and transferred to the newly organized Second Army Air Service . This was to give Second Army some experienced units in preparation for the upcoming Meuse - Argonne offensive . By this time , the front of the IV Army Corps had moved fro Lake Lachaunssee to Éply . The 135th Aero Squadron was assigned to support the 28th Division and the left group of the Corps Artillery . The 8th Squadron was assigned to the right group of Corps Artillery ; the 7th and 92d Divisions . The 168th was assigned to training missions in the rear to familiarize its pilots and observers with the sector . When , in the discretion of the Group Commander , they became more experienced in flying over the front , the 168th was assigned morning and evening reconnaissance patrols and was assigned to the 7th Division . It carried out artillery adjustments and destruction , special reconnaissance and photographic missions . Each of the three squadrons also had an infantry liaison officer , who arranged for all artillery adjustments and submitted a daily report for all planned patrols by his division . He also coordinated all technical matters between and Squadron and assigned Division . During the Meuse - Argonne offensive , Group aircraft began to be equipped with bomb racks , and along with photographic missions , began attacking enemy traffic centers , dropping leaflets , and machine - gunning enemy infantry formations . From time to time , pilots and observers would be sent to infantry units on the line and spend two days in the trenches . A liaison school was maintained , in which personnel on the line would be trained and be demonstrated contract with airplanes , and ended with an all day infantry liaison exercise , along with a battle order . The men were taught how to signal aircraft , use of flares and fireworks , and manipulation of ground panels . Upon the formation of the VI Corps Observation Group , the 8th Aero was transferred along with the 92d Division on 23 October . On 4 November , the 85th Aero Squadron was assigned to the Group . It was initially assigned to the Manonville Airdrome , but was moved back to Toul on 10 November . Newly organized , it flew only two missions over the line prior to the Armistice . On 10 November , the 258th Aero Squadron was assigned and moved to Manonville , however the Armistice was announced the next day and it flew no combat missions with the Group . Third Army Air Service . After the Armistice with Germany and the conclusion of the war , squadron flying continued on a limited basis to keep the pilots proficient in their skills . However , the main endeavors of the Group was Army administrative paperwork . During the weeks following the signing of the Armistice , the IV Corps Observation Group was relieved from Second Army on 21 November 1918 and transferred to the new Third Army Air Service , which was assigned to the Third Army ' s march to the Rhine River and the Occupation of the Rhineland . The Group was re - organized with all of its Aero squadrons being transferred to the 2d Air Instructional Center at Tours Aerodrome on 24 November . The 12th Aero Squadron was assigned to the Group for duty in Germany on 21 November . On 20 November , Corps Headquarters began the move to Germany , moving to Mercy - le - Haut , France . This town had been held for years by the Germans . On 4 December , Headquarters moved to Euren , near Trier Germany . Corps Headquarters moved still further into Germany when orders were received to move to Coblenz on 27 December . Upon arrival , the Headquarters we assigned to Fort Kaiser Alexander ) for billeting and vehicle garaging , which was formerly used by the German Garrison . Offices were set up in Third Army Headquarters Building . Upon the command ' s arrival in Germany , an airfield was constructed on the former parade ground of Fort Kaiser Alexander for aircraft squadrons being assigned to Coblenz . At Coblenz , the Group co - occupied the airfield with several squadrons assigned directly to Third Army Air Service . IV Corps Observation Group consisted of the Headquarters Squadron , 12th Aero Squadron , and the 4th Photo Section . The 2d Balloon Company was located remotely at Euren . The group established an infantry liaison school at Coblenz in January 1919 . The mission of the school was to train infantry units in displaying panels by the front line troops , the use of pyrotechnics as employed to signal from the ground to aircraft and from the aircraft to the ground . Artillery units were trained in the use of aircraft for adjusting barrages . As many officers and non - commissioned officers as possible were taken up in airplanes to view the exercises . Radio officers were taken up to perform duties in actual exercises . In addition , another important mission at Coblenz was the testing and evaluation of captured German aircraft . The intelligence and engineering departments analyzed their design and construction , as well as dis - assembling of German aircraft for evaluation . Pilots of the various squadrons at Coblenz , especially those with a background in aeronautical engineering along with the 12th flew these aircraft and evaluated their flight characteristics and tested them for performance for strengths and weaknesses . On 15 April 1919 the Third Air Service Squadrons at Coblenz were ordered demobilized , and the IV Corps Observation Group was ordered moved to Sinzig Aerodrome , a new base set up by Third Army . At Sinzing the Group received replacement squadrons which were transferred from Toul , those being the 85th , 278th and 354th , the 85th formerly being assigned to the Group in France . After a considerable amount of work , training re - commenced at Sinzing on 5 May 1919 . A week later , the entire Third Army Air Service , excepting that of the III Corps 138th Aero Squadron , one air park , and one construction squadron were relieved from further duty with the Third Army on 12 May 1919 , and ordered to proceed to the Services of Supply 1st Air Depot at Colombey , France , for demobilization . Headquarters personnel were subsequently assigned to the Commanding General , Services of Supply and ordered to report to one of several staging camps in France . There , personnel awaited scheduling to report to one of the Base Ports in France for transport to the United States and subsequent demobilization and return to civilian life .