Ihlefeld was born on 1 June 1914 in Pinnow, at the time in the Province of Pomerania, a province of the Kingdom of Prussia, the son of a farm laborer. Following a machinist vocational education, he volunteered for military service in the Reichsheer on 1 April 1933.
Following a machinist vocational education, he volunteered for military service in the Reichsheer on 1 April 1933.
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). From February–July 1938, he claimed nine aerial victories, two remained unconfirmed. For his service in Spain, he was awarded the Spanish Cross in Gold with Swords.
Ihlefeld participated in the Invasion of Poland and the Battle of France with the Jagdgeschwader 77 (JG 77—77th Fighter Wing). During the height of the Battle of Britain on 13 September 1940, he was awarded the Knight's Cross of the Iron Cross after 21 aerial victories. Ihlefeld, who had been appointed group commander of I. Gruppe of JG 77 in September 1940, fought in the Balkan Campaign and in Operation Barbarossa, the invasion of the Soviet Union. After 40 aerial victories, he was awarded the Knight's Cross of the Iron Cross with Oak Leaves on 27 June 1941. Ten months later, following his 101st aerial victory of the war, Ihlefeld was awarded the Knight's Cross of the Iron Cross with Oak Leaves and Swords on 24 April 1942.
On 22 June 1942, Ihlefeld was appointed wing commander of Jagdgeschwader 52 (JG 52—52nd Fighter Wing). He was injured in combat on 22 July 1942 and, after convalescence, was given a training command. On 21 July 1943, he was tasked with leadership of a high-flying de Havilland Mosquito intercept unit, the Jagdgeschwader 25 (JG 25—25th Fighter Wing) in Defense of the Reich. This unit failed to achieve its objective and was disbanded in late 1943. On 20 May 1944, he took command of Jagdgeschwader 1 (JG 1—1st Fighter Wing) and participated in Operation Bodenplatte. In the final weeks of the war, the Geschwader was equipped with the Heinkel He 162, a single-engine, jet-powered fighter aircraft. Ihlefeld died on 8 August 1995 in Wennigsen, Lower Saxony.
