Flying with this wing, Eder claimed his first aerial victory on 22 June 1941, the first day of Operation Barbarossa, the German invasion of the Soviet Union.

Kompanie (4th company) of Fliegerausbildungsregiment 62 (62nd Flight Training Regiment) in Quedlinburg in the Harz region, he then attended the Luftkriegsschule 2 (LKS 2—2nd air war school) at Berlin-Gatow.

Gruppe of JG 51 was withdrawn from the Channel Front in early June 1941 and ordered to Dortmund where the unit was reequipped with the Bf 109 F series.

[4] On the first day of the invasion, Eder claimed his first two aerial victories, a Polikarpov I-16 fighter and a Tupolev SB bomber shot down 09:23 and 09:35 respectively.

Gruppe was moved to an airfield at Stara Bychow, approximately 50 kilometres (31 miles) south of Mogilev on the Dnieper on 12 July.

That day, the Gruppe flew multiple combat air patrols in support of the German beachhead on the eastern bank of the Dnieper in the area between Mogilev and Smolensk.

Gruppe was moved to an airfield at Schatalowka, present-day Shatalovo air base, 40 kilometers (25 miles) southeast of Smolensk.

[13] Eder suffered a skull fracture and following convalescence, he was posted to the Jagdfliegerschule 2 (fighter pilot school) at Zerbst on 1 November 1941.

[15] JG 2 was based in northern France and fought against the United States Army Air Forces (USAAF) under the leadership of Geschwaderkommodore (wing commander) Major Walter Oesau.

The Gruppe operated from various airfields in Brittany, France, providing fighter protection for the German U-boat bases along the Atlantic coast.

[17] Eder claimed his first aerial victory on the Western Front on 30 December when he shot down a Boeing B-17 Flying Fortress bomber on a mission to bomb Lorient.

[18] Together with Mayer, Eder developed the head-on attack as the most effective tactic against the Allied daylight heavy combat box formations of B-17s and Consolidated B-24 Liberator bombers.

[23] On 13 February, the Royal Air Force (RAF) Fighter Command targeted the west coast of Pas-de-Calais with three "Rodeos" and one "Circus".

On 15 February, Eder was appointed its Staffelkapitän (squadron leader) of this newly created Staffel and tasked with bringing it to operational readiness.

[30] Following combat with a B-17, he was injured by the return fire but managed to make a forced landing of his Bf 109 G-4 (Werknummer 14988) at Beaumont-le-Roger airfield.

Staffel operated autonomously from other Luftwaffe units and claimed a B-17 bomber and a Republic P-47 Thunderbolt fighter shot down for the loss of three aircraft and two pilots killed in action.

That day, 886 heavy-bombers escorted by 980 fighter aircraft, targeted the hydrogenation factories at Leuna, Merseburg, Böhlen, Zeitz and Brüx, present-day Most in the Czech Republic.

Gruppe of JG 1, with a strength of 32 Fw 190 fighters under the leadership of Eder, relocated from Störmede to an airfield at Montdidier, France.

[51] The following day, the Gruppe flew its first combat missions during the Normandy campaign, losing two aircraft without claiming any aerial victories.

Gruppe in an anti shipping mission against the Allied landing fleet near Deauville and Trouville on southern bank of the Baie de la Seine.

[55] Attacking Allied armour near Dreux on 17 August Eder shot down a Spitfire at low level; it crashed between two M4 Sherman tanks, destroying them.

Gruppe of JG 26 after the unit's former Gruppenkommandeur Hauptmann Emil Lang was killed in action against USAAF Thunderbolts over St Trond.

[60] It is difficult to establish the exact number of aerial victories claimed by Eder while flying the Me 262 as various sources provide contradicting information.

[61] According to Harvey, Eder claimed his first aerial victory on the Me 262 on 6 October when he shot down a Lockheed P-38 Lightning F-5 reconnaissance aircraft from the 7th Photographic Group.

[64] Bley was killed in a flying accident on 28 October when his Me 262 A-1 (Werknummer 110481) suffered engine failure following a bird strike during takeoff.

[68] Harvey states that on 11 November, leading five Me 262s, Eder claimed two B-17 bombers and a North American P-51 Mustang escort fighter in combat near Frankfurt.

[75] On 9 February, during an attack of the Eighth Air Force on synthetic oil plants and transportation, Eder shot down a B-17 bomber.

[82] Eder befriended and confirmed two aerial victories claimed by First Lieutenant Urban L. Drew of the USAAF 375th Fighter Squadron.

Eder, who had observed the combat from the ground, confirmed these two claims after the war, resulting in the presentation of the Air Force Cross in May 1983.

[86] According to Boehme, Eder was credited with eleven aerial victories flying the Me 262 in the timeframe 1 October 1944 until 1 January 1945, bringing his total to 64 claims.