Trenkel served in Jagdgeschwader 52 during the Battle of Britain. From February to June 1942, he was assigned to Jagdgeschwader 77 only to be transferred back to JG 52, taking command of the 2. Staffel. In 1944 he was forced to bail out five times within ten days. On 14 July 1944, Trenkel was credited with his 100th aerial victory. He was the 83rd Luftwaffe pilot to achieve the century mark. On 16 October 1944, JG 52 lost six aircraft in combat with the French Armée de l'AirNormandie-Niemen fighter regiment serving on the Eastern Front. One of the pilots shot down was Trenkel who survived by bailing out. Trenkel and other soldiers of JG 52 surrendered to the 90th US Infantry Division near Písek on 8 May 1945 and became a prisoner of war. The soldiers were initially interned at a POW camp at Strakonice where on 14 May, Trenkel married his fiancé Ida Sehnal who was among the civilian refuges. The wedding ceremony was held by Oberst Hermann Graf. The witnesses to the wedding were MajorAdolf Borchers and Hauptmann Erich Hartmann. On 15 May, Trenkel and most of the JG 52 personnel were handed over by the American forces to the Soviet Union.
Summary of career
Aerial victory claims
According to Spick, Trenkel claimed 138 aerial victories in over 500 combat missions, all but one on the Eastern Front. Matthews and Foreman, authors of Luftwaffe Aces — Biographies and Victory Claims, researched the German Federal Archives and found records for 138 aerial victory claims, plus three further unconfirmed claims. This figure includes 131 aerial victories on the Eastern Front and one Western Allies four-engined bomber. Victory claims were logged to a map-reference, for example "PQ 59191". The Luftwaffe grid map covered all of Europe, western Russia and North Africa and was composed of rectangles measuring 15 minutes of latitude by 30 minutes of longitude, an area of about. These sectors were then subdivided into 36 smaller units to give a location area 3 × 4 km in size. south of Liuboml ! colspan="10" | – 2. Staffel of Jagdgeschwader 52 – Eastern Front — September 1944 – April 1945