Kaindl joined the army during the Weimar Republic in May 1920 and served until May 1932, leaving with the rank of sergeant. He worked briefly for a bank in the city of Donauwörth until August 1932, when he took an administrative position with the Reichskuratorium für Jugendertüchtigung (Reich Board for Youth Fitness). He joined the SS in July 1935 (SS no. 241,248) and the Nazi Party in May 1937 (party no. 4.390.500). In November 1939, he was assigned an administrative position in the SS-Totenkopf Division. He was then transferred to the administrative department of the Inspectorate of Concentration Camps headed by Richard Glücks. Kaindl's next transfer was to Sachsenhausen, where he served as commandant until the evacuation of the camp on 22 April 1945.
He was captured by the Red Army and was arraigned in the Sachsenhausen trial held by the Soviet Military Tribunal in the city hall of Pankow, Berlin in October 1947. He was charged along with Sachsenhausen record keeper, Gustav Sorge, punishment Blockführer, Kurt Eccarius, camp doctor, Heinz Baumkötter, ten other SS officers, one civil servant and two prisoner Kapos, including Paul Sakowski who served as the crematorium foreman and camp hangman from 1941 to 1943.
|Kaindl's Military Promotions|
|1 July 1935||SS-Untersturmführer|
|20 April 1936||SS-Obersturmführer|
|30 January 1938||SS-Sturmbannführer|
|30 January 1939||SS-Obersturmbannführer|
|9 November 1943||SS-Standartenführer|
- Ernst Klee, Willi Dressen and Volke Riess (editors), "Those Were the Days": The Holocaust Through the Eyes of the Perpetrators and Bystanders, London, Hamish Hamilton, 1991; published in the USA under the title "The Good Old Days": The Holocaust as Seen by Its Perpetrators and Bystanders, Old Saybrook, CT, Konecky and Konecky, 1991 ISBN 1-56852-133-2
- Johannes Tuchel: Konzentrationslager. Band 39 von Konzentrationslager: Organisationsgeschichte und Funktion der Inspektion der Konzentrationslager 1934-1938. H. Boldt, Boppard am Rhein 1991, ISBN 3-7646-1902-3.