[4] World War II in Europe had begun on Friday 1 September 1939 when German forces invaded Poland.

Gruppe of JG 3 was considered operationally ready and transferred to Detmold Airfield where it was tasked with defending Germany's western border during the "Phoney War".

Gruppe was ordered to Dieppe on 29 June where the unit was tasked with patrolling the French coast at the English Channel.

[7] Beyer claimed his first aerial victory on 14 August 1940 during the Battle of Britain with the Royal Air Force (RAF).

Gruppe flew a combat air patrol to the area of Folkestone and Dover where they encountered a formation of Hawker Hurricane fighters.

[8] He claimed his second aerial victory on 5 September, a Supermarine Spitfire fighter shot down on a mission over southern England.

Two days later on 7 September, the Luftwaffe launched Operation "Loge", 350 bombers escorted by 648 fighters, attacked various targets in the greater London area.

These air elements supported Generalfeldmarschall Gerd von Rundstedt's Heeresgruppe Süd (Army Group South), with the objective of capturing Ukraine and its capital Kiev.

Gruppe moved to an airfield at Pavlohrad, supporting German forces fighting in the Third Battle of Kharkov.

Gruppe of JG 3 was officially created on 1 June 1943 at Neubiberg Airfield and Beyer was selected as its first Gruppenkommandeur (group commander).

[19] The Gruppe was initially equipped with the Messerschmitt Bf 109 G-6, some carrying a pair of 20 mm MG 151/20 cannons installed in conformal gun pods under the wings.

Beyer was not given much time to prepare his pilots for combat, already in mid-June, the Gruppe was ordered to Italy to fight in the Mediterranean theater.

[22] Beyer claimed his first aerial victory in this theater of operations on 19 July when he shot down a Supermarine Spitfire fighter.

Luftwaffe fighter pilots claimed four bombers shot down, including one by Beyer who was credited with his 82nd aerial victory.

[27] The Gruppe flew its first combat mission against United States Army Air Forces (USAAF) on 19 December.

[30] Flying Bf 109 G-6 (Werknummer 411036—factory number), he was chased by Spitfire fighters and collided with a tree south of Liège.

[31] Beyer was buried with military honors at Venlo on 17 February and later reinterred at the Ysselsteyn German war cemetery.

Gruppe was temporarily passed to Hauptmann Heinz Lang before command was officially handed to Major Friedrich-Karl "Tutti" Müller on 26 February.