World War II in Europe began on Friday 1 September 1939 when German forces
invaded Poland. Seiler's unit was kept back and on 13 September, it formed the nucleus of the newly created I.
Gruppe of
Jagdgeschwader 54 (JG 54—54th Fighter Wing) which had been placed under command of
Major Hans-Jürgen von Cramon-Taubadel. In consequence, Seiler's 1.
Staffel was renamed 1.
Staffel of JG 54. On 1 November, the
Gruppe was transferred to
Böblingen to patrol the southernmost region of the French-German border. Seiler claimed his first victory of the war on 10 January 1940, shooting down a French reconnaissance
Potez 63 southwest of Freiburg. For this, he was awarded the
Iron Cross 2nd Class () on 20 January. He claimed a second aerial victory on 7 April west of
Strasbourg, a French
Morane-Saulnier M.S.406 fighter. However he scored no further in the subsequent
Battle of France, when his unit covered the
Panzer advance through the
Ardennes forests and later over the
Dunkirk bridgehead. Pulled out early, back to occupied Netherlands as the campaign wound down, I.
Gruppe of JG 54 was then one of the first units to re-occupy the
Pas de Calais, in early August 1940 in anticipation of the upcoming
Battle of Britain. On a bomber escort mission over Dover on 5 August 1940, Seiler claimed his third aerial victory, shooting down a
Supermarine Spitfire over the
English Channel. He was then shot down in his Bf 109 E-4 and severely injured. Taking to his parachute over the English Channel, Seiler was rescued and hospitalized, but was out of action for over 6 months. In consequence, command of 1.
Staffel was briefly passed on to
Oberleutnant Friedrich Rumpf before
Oberleutnant Gerhard Ködderitzsch took command of the
Staffel. On 1 December 1940, Seiler was promoted to
Hauptmann (captain).
Invasion of the Soviet Union Operation Barbarossa, the German invasion of the
Soviet Union, began on 22 June 1941. In the fortnight prior, JG 54 had been moved to an airfield in Lindenthal near Rautenberg,
East Prussia, present-day Uslowoje in
Kaliningrad Oblast. Tasked with supporting
Army Group North in its advance through the
Baltic states towards
Leningrad, the unit began combat operations shortly afterwards. On the first day of combat operations, Seiler claimed three aerial victories, thereby doubling his total to six. Seiler, who had served with the
Gruppenstab (headquarters unit) of I.
Gruppe since his convalescence, was again appointed
Staffelkapitän of 1.
Staffel on 27 June. He replaced
Oberleutnant Adolf Kinzinger who had been killed in a flight accident that day. Over the next few weeks, I.
Gruppe leap-frogged to new airbases across the Baltic States. The
Gruppe had moved to
Schaulen, now Šiauliai, on 25 June, to Birži, located approximately southwest of
Jēkabpils, and to
Alt-Schwanenburg, now Gulbene, on 5 July. Here the following day, Seiler claimed three
Tupolev SB-3 bombers shot down. On 29 July, I.
Gruppe moved to a makeshift airfield named Malaja Owsischtschi located near Lake Ozero Samro () east of
Lake Peipus where they remained until 24 August. Here, the
Gruppe supported German forces in the attack on Leningrad. Here on 20 August, Seiler had been awarded the
Honor Goblet of the Luftwaffe (). On 8 September, I.
Gruppe moved to an airfield at
Siverskaya, located approximately south of Leningrad. The next day, Seiler and his
wingman flew a
combat air patrol and intercepted a flight of I-16 fighters near
Krasnoye Selo where Seiler claimed an I-16 shot down. Flying in a northwestern direction, they flew over a Soviet airfield at Nizinskoye, located approximately northwest of Krasnoye Selo, where 5 IAP (Istrebitelny Aviatsionny Polk— or Fighter Aviation Regiment) led by
Stárshiy Leytenánt Mikhail Bagryantsev was based. Two
Lavochkin-Gorbunov-Gudkov LaGG-3 and two
Mikoyan-Gurevich MiG-3 took off to intercept the German fighters. In this encounter, Seiler shot down Bagryantsev to take his total to 25 aerial victories. On 11 September, Seiler made an
emergency landing at Siverskaya after his Bf 109 F-2 (
Werknummer 12692—factory number) had been damaged by enemy fire.
Group commander On 1 October 1941, Seiler was appointed
Gruppenkommandeur (group commander) of III.
Gruppe of JG 54. He replaced
Hauptmann Arnold Lignitz who had been posted as
missing in action after he had been shot down over Leningrad the day before. Command of his former 1.
Staffel was then passed to
Oberleutnant Heinz Lange. At the time, III.
Gruppe was also based at Siverskaya. Seiler, who remained in command of III.
Gruppe for nearly one and a half years, was awarded the
German Cross in Gold () on 15 October. On 20 December, having flown 200 missions, Seiler was awarded the
Knight's Cross of the Iron Cross () for 42 aerial victories claimed during World War II. In spring 1942
Geschwaderkommodore (Wing Commander)
Hannes Trautloft had the idea for
night fighter interceptions of Soviet night-harassment raids on moonlit nights. A great success, they claimed 56 victories for no losses. During these nocturnal combat missions in June 1942, Seiler claimed 15 aerial victories. On the night of 11/12 June, he claimed two
Polikarpov R-5 bombers shot down. In the night of 14/15 June, he was credited with the destruction of two further R-5 bombers destroyed. The following night, Seiler was credited with shooting down two R-5 bombers and a single
Yakovlev Yak-1 fighter. On the night of 22/23 June, he claimed two
Lisunov Li-2, also known as a PS-84, destroyed. On the night of 25/26 June, two R-5 bombers were claimed by him. Seiler claimed his last nocturnal aerial victories, two R-5 bombers, on the night of 27/28 June. On 30 November, Seiler relocated III.
Gruppe to
Smolensk where they arrived on 3 December. Here, the
Gruppe supported German forces fighting in the
Battle of Stalingrad. In early 1943, III.
Gruppe rotated back to the
Western Front as part of
Adolf Galland's mis-guided plan to swap units between the Western and Eastern Fronts in exchange for I.
Gruppe of
Jagdgeschwader 26 "Schlageter" (JG 26—26th Fighter Wing). On 1 March 1943, Seiler was also promoted to
Major (major).
Defense of the Reich In mid-February 1943, III.
Gruppe of JG 54 was withdrawn from the Eastern Front and ordered to
Vendeville, France where it was subordinated to the
Geschwaderstab of JG 26. The
Gruppe was equipped with the Bf 109 G-4 armed with 20 mm
MG 151/20 cannons installed in conformal
gun pods under the wings. The original plan was to exchange JG 26 which had been fighting on the Western Front with JG 54. The plan was cancelled in March. Instead of III.
Gruppe of JG 54 returning to the Eastern Front, the
Gruppe was ordered to
Bad Zwischenahn on 25 March and then to
Oldenburg Airfield two days later. Here, the
Gruppe was subordinated to the
2. Jagd-Division (2nd Fighter Division) which was fighting in
defense of the Reich. On 17 April, III.
Gruppe flew its first combat mission in defense of the Reich. That day, the
United States Army Air Forces (USAAF)
VIII Bomber Command, later renamed to Eighth Air Force, attacked the
Focke-Wulf factory in
Bremen. The
Gruppe was
scrambled at 12:29. At 12:40 approximately 120 to 150
Boeing B-17 Flying Fortress bombers were encountered west of
Wilhelmshaven. Due to evasive maneuvering of the bombers and the heavy defensive gunfire, the
Gruppe initially failed to attack the bombers head-on. At 13:00, III.
Gruppe made their first head-on attack while the leading bombers of the
91st and
306th Bombardment Group made their bomb-run. In this attack, Seiler shot down one of the B-17 bombers over Bremen. The
Gruppe kept pursuing the bombers and claimed four further bombers shot down, one of which was not confirmed. On 1 May, Seiler was made the new
Gruppenkommandeur of I.
Gruppe of JG 54, flying the
Focke-Wulf Fw 190. He replaced
Hauptmann Gerhard Koall who temporarily led the
Gruppe after
Major Hans Philipp was transferred to take command of
Jagdgeschwader 1 (JG 1—1st Fighter Wing) fighting in defense of the Reich. In consequence, command of III.
Gruppe was given to
Hauptmann Siegfried Schnell.
Eastern Front When Seiler took command of I.
Gruppe they were based at
Krasnogvardeysk, present-day Gatchina, and unseasonably bad weather limited flight operations for the next few weeks. In early July, the
Gruppe was ordered to
Oryol in preparation of
Operation Citadel. There, I.
Gruppe supported
Army Group Centre during the
Battle of Kursk cover over the northern attack under control of
Luftflotte 6 (Air Fleet 6). On the opening day of the offensive, 5 July, he claimed 5 aerial victories, making him an "
ace-in-a-day", to take his tally to 97. The following day he claimed two further aerial victories. Eager to reach the magic 'century', he chased and shot down a
Bell P-39 Airacobra fighters from the 30 GvIAP (Guards Fighter Aviation Regiment—
Gvardeyskiy Istrebitelny Aviatsionny Polk). However immediately afterward he was himself shot and forced to bail out from his Fw 190 A-5 (
Werknummer 1341) badly wounded over enemy territory east of
Ponyri, midway between Orel and Kursk. His injuries sustained rendered him unfit for further combat operations for the rest of the war. Seiler was the 44th Luftwaffe pilot to achieve the century mark. Due to his injuries sustained, he was temporarily replaced by
Oberleutnant Hans Götz as commander of I.
Gruppe before
Hauptmann Gerhard Homuth took command on 1 August. In recognition of his long service and command in JG 54, Seiler was awarded the
Knight's Cross of the Iron Cross with Oak Leaves () on 2 March 1944. The presentation was made by
Adolf Hitler on 4 April 1944 at the
Führerhauptquartier (Führer Headquarter) at the
Berghof in
Berchtesgaden. Also present at the award ceremony were
Gerhard Barkhorn, for the Swords to his Knight's Cross, and
Erich Hartmann,
Walter Krupinski,
Kurt Bühligen,
Horst Ademeit,
Hans-Joachim Jabs, Dr.
Maximilian Otte,
Bernhard Jope and
Hansgeorg Bätcher from the bomber force, and the Flak officer
Fritz Petersen, all destined to receive the Oak Leaves. On 16 May 1944, following his convalescence, Seiler was appointed
Geschwaderkommodore of the fighter-pilot training unit
Jagdgeschwader 104 (JG 104—104th Fighter Wing). He served in this capacity until the
end of World War II in Europe. ==Later life==