Eisenach was appointed Staffelkapitän of 3. Staffel of Jagdgeschwader 54 on 17 April 1943. He replaced HauptmannGerhard Koall in this function who was transferred. On 8 July 1943, Eisenach was wounded in his Focke Wulf Fw 190 A-5 during combat with Douglas A-20 Havoc bombers northeast of Panino. During his convalescence, he was temporarily replaced by OberleutnantRobert Weiß as Staffelkapitän. On 18 December, he was again injured and shot down. On this occurrence, his Fw 190 A-6 was shot down by anti-aircraft artillery northwest of Gorodok, south of Nevel. On 8 August 1944, Eisennach was appointed Gruppenkommandeur on I. Gruppe of JG 54. He succeeded HauptmannHorst Ademeit who was killed in actionthe day before. Soviet forces launched the Baltic Offensive on 14 September 1944. Thad day, Eisenach claimed his 100th victory on 14 September 1944 by shooting down an IL-2 Sturmovik. That day, he became an "ace-in-a-day" claiming nine aerial victories, include five Ilyushin Il-2 ground attach aircraft and four Petlyakov Pe-2 twin-engined dive bombers. He was the 90th Luftwaffe pilot to achieve the century mark. Eisenach was awarded the Knight's Cross of the Iron Cross on 10 October for 107 aerial victories. Eisenach re-joined the military service of the Bundeswehr in 1956. He left the service in 1974 with the rank of Oberstleutnant.
Summary of career
Aerial victory claims
According to Spick, Eisenach claimed 129 aerial victories in 319 combat missions, all of which on the Eastern Front. Matthews and Foreman, authors of Luftwaffe Aces — Biographies and Victory Claims, researched the German Federal Archives and also found confirmed records for 129 aerial victories for 154 claims filed. Victory claims were logged to a map-reference, for example "PQ 00253". The Luftwaffe grid map covered all of Europe, western Russia and North Africa and was composed of rectangles measuring 15 minutes of latitude by 30 minutes of longitude, an area of about. These sectors were then subdivided into 36 smaller units to give a location area 3 × 4 km in size.