Following flight training, he volunteered for service with the Condor Legion during the Spanish Civil War where he was assigned to Jagdgruppe 88 (J/88—88th Fighter Group).

Ihlefeld, who had been appointed Gruppenkommandeur (group commander) of I. Gruppe of Jagdgeschwader 77 (JG 77—77th Fighter Wing) in September 1940, fought in the aerial battles of the Balkan Campaign.

On 21 July 1943, he was tasked with leadership of a high flying de Havilland Mosquito intercept unit called Jagdgeschwader 25 (JG 25—25th Fighter Wing) in Defense of the Reich.

(J)—1st fighter group) of Lehrgeschwader 2 (LG 2—2nd Demonstration Wing), an operational training unit tasked with the evaluation of new types of aircraft and tactics.

Ihlefeld flew his first combat missions over Poland and was awarded the Iron Cross 2nd Class (Eisernes Kreuz zweiter Klasse) on 26 September 1939.

On this mission, 11 Messerschmitt Bf 109s encountered two Armée de l'air (French Air Force) Morane-Saulnier M.S.406 fighter aircraft.

(J)/LG 2 was tasked with flying escort fighter missions for Kampfgeschwader 2 (KG 2—2nd Bomber Wing) attacking British shipping in the English Channel.

On the third mission of the day (16:25 – 17:20), escorting a flight of Dornier Do 17 bombers to their targets, Ihlefeld claimed his fourth victory of the war, a Hawker Hurricane fighter aircraft shot down at 16:30.

In the following four weeks, the Gruppe received a period of rest and the aircraft were given a maintenance overhaul prior to moving back to the Channel Front, to an airfield at Marck, east of Calais, on 8 August.

17) on 1 August 1940; the strategic objective was to engage and defeat the RAF so as to achieve air superiority in preparation for Operation Sea Lion (Unternehmen Seelöwe), the proposed amphibious invasion of Great Britain.

That day, it flew to the airfield at Calais-Marck and was subordinated to the Stab (headquarters unit) of Jagdgeschwader 52 (JG 52—52nd Fighter Wing).

[42] On 5 February 1941, the RAF began the Circus offensive against the Luftwaffe, a series of attacks flown by heavily escorted bombers targeted the coastal region in northern France.

(J)/LG 2 combated Spitfires 20 kilometers (12 miles) north of Cap Gris Nez and Ihlefeld again claimed one of his opponents shot down.

Based at Radomir in Bulgaria, the unit was subordinated to Generaloberst (Colonel General) Wolfram Freiherr von Richthofen's VIII.

(J)/LG 2 primary targets in this campaign were various Jugoslovensko Kraljevsko Ratno Vazduhoplovstvo (JKRV—Yugoslav Royal Air Force) airfields in the greater Skopje area.

During one of these missions, strafing the railway up the Vardar valley and an airfield near Niš, Ihlefeld was shot down in his Bf 109 E-7 (Werknummer 2057—factory number) by anti-aircraft artillery and was captured by Yugoslavian soldiers.

[53][Note 5] The airfield at Niš was practically deserted and Ihlefeld had been hit by small arms fire and was slightly wounded in the head.

On the first mission of the day, 34 Bf 109 provided fighter escort for two Gruppen of KG 27 in support of the advancing German ground forces.

[73][84] On 1 June 1943, the Luftwaffe ordered the creation of Jagdgeschwader Nord (JG Nord—Northern Fighter Wing) at Staaken, located approximately 18 kilometers (11 miles) northwest of Berlin.

[92] With the increasing number of daytime attacks flown by United States Air Force (USAAF), JG 25 was also deployed in defense of the Reich missions.

Ihlefeld claimed his only aerial victory with JG 25 on 13 November during an attack flown by the USAAF VIII Bomber Command on Bremen.

[100] Ihlefeld participated and led JG 1 in Operation Bodenplatte, the failed attempt to cripple Allied air forces in the Low Countries.

The objective of Bodenplatte was to gain air superiority during the stagnant stage of the Battle of the Bulge and dates back to meeting held on 16 September 1944.

Ihlefeld threatened to court martial Major Günther Capito, the new commander of I. Gruppe, for such a disastrous loss but was unable to during the transferring to the Eastern Front.

Gruppe was sent to Schröttersburg, present-day Płock, located on the Vistula river approximately 70 kilometers (43 miles) northwest of Warsaw.

[110] As Geschwaderkommodore, Ihlefeld was ordered to Berlin on 22 January 1945 and attended the meeting with Reichsmarschall Hermann Göring which was later dubbed the Fighter Pilots' Mutiny.

The meeting was held at the Haus der Flieger in Berlin and was attended by a number of high-ranking fighter pilot leaders which included Ihlefeld, Günther Lützow, Hannes Trautloft, Hermann Graf, Gerhard Michalski, Helmut Bennemann, Kurt Bühligen and Erich Leie, and their antagonist Göring supported by his staff Bernd von Brauchitsch and Karl Koller.

The fighter pilots, with Lützow taking the lead as spokesman, criticized Göring and made him personally responsible for the decisions taken which effectively had led to the lost air war over Europe.

Originally the Luftwaffe had planned to create a new formed unit, Jagdgeschwader 80 (JG 80—80th Fighter Wing), staffed with pilots of the National Socialist Flyers Corps (NSFK—Nationalsozialistisches Fliegerkorps) and the Flieger-HJ, the flying members of the Hitler Youth.

[115] Following World War II, Ihlefeld did not rejoin the military service of the German Air Force, at the time referred to as the Bundesluftwaffe, of the Federal Republic of Germany.