World War II in Europe had begun on Friday, 1 September 1939, when German forces
invaded Poland. At the time, Welter served with
Flieger-Ausbildungsregiment 71 (71st Flight Training Regiment) which was based in
Sorau, present-day Żary, and
Guben, now the
Cottbus-Drewitz Airport.
Flieger-Ausbildungsregiment 71 was subordinated to the
Flugzeugführerschule A/B 3 (FFS A/B 3—flight school) where Welter served as a flight instructor. On 19 March 1940, Welter was transferred to
Flieger-Ausbildungs-Regiment 63 (63rd Flight Training Regiment) which was based in
Marienbad, present-day Mariánské Lázně, as an instructor. There, he was promoted to
Feldwebel (sergeant) on 1 August 1940. In November, Welter married Ingrid Katharina Emma Green. The marriage produced two children, a daughter and a son. For his service as a flight instructor, he was awarded the
War Merit Cross 2nd Class with Swords () on 23 March 1941. In June 1942, he transferred to
Flugzeugführerschule A/B 121 (FFS A/B 121—flight school) at
Straubing. Here, Welter was promoted to the rank of
Oberfeldwebel (staff sergeant) on 1 October 1942 and again served as a flight instructor until 10 August 1943 when he was transferred to
Blindflugschule 10 (school for instrument flight training) in
Altenburg. At Altenburg, he also received his pilot license for night flying (), required for flying night fighter missions.
Night fighter career Following the 1939 aerial
Battle of the Heligoland Bight,
Royal Air Force (RAF) attacks shifted to the cover of darkness, initiating the
Defence of the Reich campaign. By mid-1940,
Generalmajor (Brigadier General)
Josef Kammhuber had established a night
air defense system dubbed the
Kammhuber Line. It consisted of a series of control sectors equipped with
radars and
searchlights and an associated night fighter. Each sector named a
Himmelbett (canopy bed) would direct the night fighter into visual range with target bombers. In 1941, the Luftwaffe started equipping night fighters with airborne radar such as the
Lichtenstein radar. This airborne radar did not come into general use until early 1942. On 2 September 1943, Welter was transferred to 5.
Staffel (5th squadron) of
Jagdgeschwader 301 (JG 301—301st Fighter Wing), a
night fighter squadron that experimented with the use of largely radar-less single-seat
Focke-Wulf Fw 190 A-5 and Fw 190 A-6 fighter aircraft by night, often equipped with the
FuG 350 Naxos radar detector, used in the form of German night-fighter operations without AI radar — due to
Düppel interference from RAF Bomber Command aircraft. These free ranging interception operations were called
Wilde Sau (wild boar). On his first
Wilde Sau intercept mission against Allied bombers on the night of 22/23 September 1943, Welter claimed two Allied four-engine bombers shot down in the vicinity of
Hanover. He shot down two further bombers on his third mission on the night of 3/4 October 1943. That night, he was credited with the destruction of two
Handley Page Halifax bombers near
Kassel. The
30. Jagddivision (30th Fighter Division) submitted Welter for a preferential promotion to
Leutnant (second lieutenant) on 7 January 1944. The recommendation was approved and as of 1 February 1944, Welter served as an officer. By the beginning of April, he had accumulated 17 victories in only 15 missions. Subsequently, on 10 May 1944 Welter was awarded the
German Cross in Gold (). Welter was transferred to 5.
Staffel of
Jagdgeschwader 300 (JG 300—300th Fighter Wing) on 7 July 1944. In July, Welter claimed two
United States Army Air Forces (USAAF)
Boeing B-17 Flying Fortress four-engined bombers and three
North American P-51 Mustangs, two of which claimed on 19 July between
Munich and
Memmingen, shot down by day. From 25 July 1944, Welter served with 1.
Staffel of
Nachtjagdgruppe 10 (NJGr 10) performing further
Wilde Sau missions. On the night of 25/26 August, Welter claimed his first
de Havilland Mosquito twin-engine bomber shot down. That night, the RAF did not report the loss of a Mosquito over Germany. However, the combat report of
No. 692 Squadron of that night shows that Mosquito serial
MM140 on its mission to bomb Berlin came under attack by a
Messerschmitt Bf 109 which hit the starboard wing, bursting the tire. Although the Mosquito returned to England, the aircraft crash landed at
RAF Woodbridge and was damaged beyond repair. Welter then claimed four RAF
Avro Lancaster four-engine heavy bombers shot down on the night of 29/30 August 1944. All four victories were claimed west of
Stettin, two of which were not confirmed. Welter transferred to 10.
Staffel of JG 300 on 4 September 1944. 10.
Staffel of JG 300 was established to counter intrusions by the RAF's fast Mosquito twin-engined bombers, flying specially optimized for speed Bf 109 G-6/AS fighters. In September, Welter claimed seven Mosquitos downed, including one by
ramming. It is thought that during his service with 1./NJG 10 and 10./JG 300, Welter recorded 12 victories in only 18 missions. The ramming incident occurred on 13 September when Welter attacked and
collided or deliberate rammed Mosquito serial
MM280 near
Salzwedel. The Mosquito managed to fly back to Allied territory and made a
forced landing near
Brussels-Melsbroek Airfield, destroying the aircraft. On the night of 19 September 1944, according to Hinchliffe, Welter may have shot down
Wing Commander Guy Gibson who was leading a 300-bomber attack on
Mönchengladbach and
Rheydt. Gibson's Mosquito crashed near
Steenbergen in the
Netherlands. Welter was the only German pilot to have claimed a Mosquito. The claim is unlikely. Welter submitted his victory claim north of
Wittenberg in eastern Germany, some hundreds of miles away from the place Gibson's Mosquito was found. Recent research suggests that his victim was Mosquito VI serial
PZ177 of
No. 23 Squadron RAF which was shot down at west of
Bad Münder,
Holzminden. The crew, F/O. K. Eastwood and Navigator F/L. G.G. Rogers were both killed. Welter was awarded the
Knight's Cross of the Iron Cross () on 18 October 1944 for 33 victories in just 40 missions.
Flying the Messerschmitt Me 262 -equipped Me 262B-1a/U1 in the
South African National Museum of Military History.|alt=A twin engine jet aircraft pictured from front-left sitting on the ground in a hangar. The paint scheme of the aircraft is camouflage of various brown and green colours. Two antennas are protruding from the nose of the aircraft. The white number "305" is visible on the nose of the aircraft. On 2 November 1944, Welter was transferred to II.
Gruppe of
Nachtjagdgeschwader 11 (NJG 11), a reformation of his former unit. Here he was given command of a special Kommando subordinate to II./NJG 11, set up on 11 November 1944 at
Erprobungsstelle Rechlin's southern Lärz airbase (2 November 1944 – 28 January 1945), and dedicated to performing nocturnal interception with the
Messerschmitt Me 262 jet fighter of RAF Mosquitos attacking the Berlin area. Welter was promoted to
Oberleutnant (first lieutenant) on 1 December 1944. According to some sources, Welter added a Lancaster to his growing list of Mosquitos on the night of 12 December 1944, the first night victory by a jet fighter. Other sources state that his first aerial victory flying the Me 262 was claimed either on the night of 2 January 1945 or 5 January 1945. On 15 December, Welter recruited
Feldwebel Karl-Heinz Becker whom he had known from their mutual tenure with FFS A/B 121. On 28 January 1945, the unit initially known as
Sonderkommando Stamp, named after its founder
Major Gerhard Stamp and then
Sonderkommando Welter, was re-designated 10.
Staffel of NJG 11 and transferred to the airfield at Burg near
Magdeburg (28 January 1945 – 12 April 1945). The unit was equipped with Me 262 jet fighters, and tasked with intercepting Mosquito bomber aircraft of No. 8 Group RAF in the Berlin area. The Me 262 were not fitted with radar and used the aid of ground control and the searchlight defences, partially a
Wilde Sau form of night combat. Welter had claimed three aerial victories while flying the Me 262 by early February 1945. Thereafter, Welter made a string of questionable air combat claims against Mosquito aircraft in the Berlin area – three on the night of 21 February 1945 (no Mosquitoes recorded lost), and another three on the night of 2 March 1945 (one Mosquito damaged in aerial combat). 10./NJG 11 made further claims against Mosquito aircraft attacking Berlin on the nights of 21 March 1945 (three claims; one Mosquito lost), 23 March 1945 (three claims; one Mosquito lost, another damaged in aerial combat), 24 March 1945 (two claims; one Mosquito damaged in aerial combat), 27 March 1945 (two claims; two Mosquitos lost), 30 March 1945 (four claims; one Mosquito lost and another damaged in aerial combat), 2 April 1945 (one claim; one Mosquito lost), 3 April 1945 (two claims; one Mosquito lost and another damaged in aerial combat), and 19 April 1945 (two claims, no Mosquitos lost). The last known aerial combat claim by Welter occurred on the night of 3 April 1945, when a Mosquito of No. 139 Squadron RAF, was shot down over Berlin. Welter was awarded the
Knight's Cross of the Iron Cross with Oak Leaves () on 11 March 1945 for 48 victories. In early May 1945, 10./NJG 11 relocated to
Schleswig Airfield, its last relocation before the
German surrender. There, Welter was taken
prisoner of war by British forces and interrogated by the RAF. The RAF published two reports which contained information regarding the use of the Me 262 in a night fighter role. The first "
Report on G.A.F. Night Fighter System" does not mention Welter directly by name but rather refers to him as "
Commander of the Me 262 Flight". A further report named "
Report on G.A.F. Night Fighting from the interrogation of Prisoners" contains a detailed report of Welter's interrogation. In mid-1945, Welter was released from captivity. ==Later life and death==