In July 1937, Handrick was appointed Gruppenkommandeur (group commander) of Jagdgruppe 88 (18 July 1937 – 10 September 1938). This unit fought in the Spanish Civil War where he claimed five aerial victories while flying for the Legion Condor, including a Polikarpov I-15 fighter on 9 September 1937 and an Polikarpov I-16 fighter on 18 May 1938.[4] He was later awarded the Spanish Cross in Gold with Swords (Spanienkreuz in Gold mit Schwertern) on 14 April 1939 for his service in the Spanish Civil War.[5]
Handrick was then given command of I. Gruppe of Jagdgeschwader 132 "Schlageter" on 11 September 1938 after his return from Spain.[6] This unit then became I. Gruppe of Jagdgeschwader 26 "Schlageter" on 1 May 1939 which he led until 23 June 1940.[7] On 24 June 1940 command of JG 26 was handed over to Major Handrick, who passed command of I./JG 26 to Hauptmann Kurt Fischer.[8] After he left JG 26, Handrick served with the Luftwaffenmission Rumänien (Luftwaffe Mission Romania) under the command of Generalleutnant (equivalent to major general) Wilhelm Speidel.[9][10]
On 7 October, Handrick took over command of III. Gruppe of Jagdgeschwader 52 (JG 52—52nd Fighter Wing) from Hauptmann Alexander von Winterfeld who was transferred. He led this Gruppe until 23 June 1941.[11] Command of the Gruppe was then given to Major Albert Blumensaat.[12]
During World War II he was a recipient of the German Cross in Gold (Deutsches Kreuz in Gold) on 17 October 1943.[15] In March 1942, Oberstleutnant Handrick transferred to command Jagdgeschwader 5 (JG 5—5th Fighter Wing) in Norway and Northern Russia.[16] From June 1943 to June 1944 he was Jagdfliegerführer Ostmark. Then as an Oberst, he became the commanding officer of 8. Jagd-Division in Austria, a position he held until the end of the war.[17] After the war he worked in Hamburg as a representative of Daimler-Benz.[18]
Barbas, Bernd (2010). Die Geschichte der III. Gruppe des Jagdgeschwaders 52 [The History of 3rd Group of Fighter Wing 52] (in German). Eutin, Germany: Struve-Druck. ISBN978-3-923457-94-6.
Caldwell, Donald L. (1991). JG 26: Top Guns of the Luftwaffe. New York: Ivy Books. ISBN978-0-8041-1050-1.
Mathews, Andrew Johannes; Foreman, John (2015). Luftwaffe Aces — Biographies and Victory Claims — Volume 2 G–L. Walton on Thames: Red Kite. ISBN978-1-906592-19-6.
Mombeek, Eric (2011). Eismeerjäger—Zur Geschichte des Jagdgeschwaders 5—Band 4 [Fighters in the Arctic Sea—The History of the 5th Fighter Wing—Volume 4]. Linkebeek, Belgium: ASBL, La Porte d'Hoves. ISBN978-2-930546-05-6.
Patzwall, Klaus D.; Scherzer, Veit (2001). Das Deutsche Kreuz 1941 – 1945 Geschichte und Inhaber Band II [The German Cross 1941 – 1945 History and Recipients Volume 2] (in German). Norderstedt, Germany: Verlag Klaus D. Patzwall. ISBN978-3-931533-45-8.
Prien, Jochen (1995). Geschichte des Jagdgeschwaders 77—Teil 4—1944–1945 [History of Jagdgeschwader 77—Volume 4—1944–1945] (in German). Eutin, Germany: Struve-Druck. ISBN978-3-923457-29-8.
Prien, Jochen; Stemmer, Gerhard; Rodeike, Peter; Bock, Winfried (2000). Die Jagdfliegerverbände der Deutschen Luftwaffe 1934 bis 1945—Teil 1—Vorkriegszeit und Einsatz über Polen—1934 bis 1939 [The Fighter Units of the German Air Force 1934 to 1945—Part 1—Pre-War Period and Action over Poland—1934 to 1939] (in German). Eutin, Germany: Struve-Druck. ISBN978-3-923457-54-0.
Prien, Jochen; Stemmer, Gerhard; Rodeike, Peter; Bock, Winfried (2003). Die Jagdfliegerverbände der Deutschen Luftwaffe 1934 bis 1945—Teil 6/II—Unternehmen "BARBAROSSA"—Einsatz im Osten—22.6. bis 5.12.1941 [The Fighter Units of the German Air Force 1934 to 1945—Part 6/II—Operation "BARBAROSSA"—Action in the East—22 June to 5 December 1941] (in German). Eutin, Germany: Struve-Druck. ISBN978-3-923457-70-0.
Schreier, Hans (1990). JG 52 Das erfolgreichste Jagdgeschwader des 2. Weltkriegs [JG 52 The Most Successful Fighter Wing of World War II] (in German). Berg am See: K. Vowinckel. ISBN978-3-921655-66-5.