Born in Hennstedt, Ehlers volunteered for service with the Condor Legion during the Spanish Civil War where he was assigned to the ground crew of Jagdgruppe 88 (J/88—88th Fighter Group).

Due to an organizational change, his unit became part of Jagdgeschwader 1 (JG 1—1st Fighter Wing) in early 1942 and was stationed on the Western Front and fighting in Defense of the Reich.

Following his return from Spain, Ehlers received flight training at the pilot school in Salzwedel starting on 1 August.

[3] World War II in Europe began on Friday 1 September 1939 when German forces invaded Poland.

[6] He in turn, was then shot down by RAF fighters on the same day and crash-landed his Messerschmitt Bf 109 E-1 south of Valenciennes and was initially listed as missing in action, rejoining his unit shortly later.

[9] On 5 September, I. Gruppe escorted 22 Dornier Do 17 light bombers to London where Ehlers claimed another Spitfire shot down.

[12] In preparation for Operation Barbarossa, the German invasion of the Soviet Union, the I. Gruppe moved to an airfield at Dub on 18 June 1941.

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

In total, I. Gruppe claimed 36 aircraft destroyed on the ground plus further 8 aerial victories on the first day, including a Polikarpov I-16 fighter by Ehlers.

That day, Ehlers was wounded in a takeoff accident at Lutsk which destroyed his Bf 109 F-2 (Werknummer 5708—factory number).

Fighting over the battle zones over Kyiv and Kaniv on 15 August, he claimed an I-17 fighter and a V-11 ground attack aircraft shot down.

[19] On 26 August, I. Gruppe was moved to a forward airfield named Gubin located near the front at Hornostaipil.

[20] Four days later, the Gruppe flew ten combat missions, two in support of Junkers Ju 87 dive-bombers and eight to protect the bridges crossing the Dnieper near Hornostaipil.

[21] On 16 September, the bulk of I. Gruppe was ordered back to Germany while 12 pilots and 40 men from the ground staff remained on the Eastern Front and were sent to either II.

Staffel which followed in November, I. Gruppe of JG 3 was transferred from the Eastern Front to Germany for rest and re-supply.

Gruppe was reequipped with the Focke-Wulf Fw 190 A series, a radial engine powered fighter aircraft, at Woensdrecht Air Field.

[26] On 6 December, Ehlers claimed his first United States Army Air Forces (USAAF) heavy bomber shot down, his 17th aerial victory in total.

At 11:50, the Luftwaffe fighters of I. Gruppe of JG 1 intercepted a large formation of B-17 bombers in the area of Aschaffenburg.

[36] That day, VIII Bomber Command had targeted Bremen and German ship building at Bremen-Vegesack.

[37] The aircraft rammed was the B-17 "Marie Helena" from the 351st Bombardment Squadron whose entire crew was killed in the collision.

[38] That day, JG 1 lost its commanding officer, Oberstleutnant Hans Philipp, who was killed in action.

Staffel also spontaneously executed an unprecedented maneuver by ramming B-17 bombers that were returning westward from a raid against shipyards and factories in Bremen and Vegesack.

[40] On 23 October 1943, Reichsmarschall Hermann Göring, the Commander-in-Chief of the Luftwaffe, visited JG 1 at Deelen Air Field.

[43] On 17 April 1944, Ehlers was appointed Gruppenkommandeur (group commander) of I. Gruppe of JG 1, succeeding Major Rudolf-Emil Schnoor.

JG 1 was sent to intercept the bombers of the 1st Bomb Division but were engaged by the escorting fighters over the Bay of Lübeck.

During the period associated with Operation Overlord (6 June – 30 August 1944), the Gruppe claimed 50 aerial victories for the loss of 34 pilots killed, 3 taken prisoner of war, and further 13 wounded.

[52] Ehlers claimed his last aerial victory on 25 December when approximately 400 B-17 and B-24 bombers attacked German communication and transportation centers in western Germany.

[53] On 27 December 1944, Ehlers led a flight of 18 Fw 190s on a mission to cover ground troops in the Dinant-Rochefort area during the Battle of the Bulge.