Franz left the army in 1920. He entered the Saxon state police force and was assigned to an officer course in Dresden. He worked as a policeman in the cities of Plauen and Zwickau and worked as an instructor in a police school. Franz joined the Nazi Party in December 1931. From 1933 to 1938 he was chief of police in Plauen. At the beginning of World War II he was part of German occupation of Poland for a short time from September 1939 to October 1939 as Commander of the Order Police at Army Headquarters 8th. In August 1940, he joined the SS in, he was promoted to SS-Obersturmbannführer.
Just prior to Operation Barbarossa, the invasion of the Soviet Union, Franz was appointed commander of Police Regiment South. It was formed in June 1941 by combining Order Police Battalions 45, 303, and 314. The regiment was subordinated to Friedrich Jeckeln, the Higher SS and Police Leader for Army Group South in Ukraine. The regiment began executing Jewish women and children in July 1941. On 22 July, Police Battalion 314 killed 214 Jews in a settlement near Kovel, including entire families. Police Regiment 45 murdered the entire Jewish population of Shepetovka while stationed there between 26 July and 1 August. The orders came down from Franz, who had referred to an order from Heinrich Himmler. During August, the regiment murdered Jews in Slavuta, Kowel and other areas, often killing hundreds of victims per battalion per day. On 25 August, it murdered 1,153 Jews, while on 27 August, it killed 914. Later that month, the regiment perpetrated the Kamianets-Podilskyi massacre, alongside Jeckeln's staff company. The staff company did the shooting, while Police Battalion 320 cordoned off the area. The massacres resulted in the murder of thousands of Jews deported from Hungary and rounded up Ukrainian Jews. Shortly thereafter, Police Battalion 320 reported the shooting of twenty-two hundred Jews at another location north-east of Kamianets-Podilskyi. The overall Einsatzgruppen report for the operation listed 23,000 victims. In September, Police Battalion 45 participated in the murder of Jews in Berdichev, cordoning off the execution site and leading the victims to the pits where they were shot by Jeckeln's staff company. About 16,000 Jews were killed. During the massacre at Baby Yar, the same police battalion cordoned off the area, while Sondercommando 4a and a platoon of the Waffen-SS did the shooting. Police Battalion 303 participated in the massacre, as well.
Later SS career
In mid-May 1942 he assumed command of the forming 18th Mountain Police Regiment and remained in command until August 1943. From November 1943 to February 1945 he was Commander of the Order Police in Athens. In September 1944, for two months, he was promoted to the Higher SS and Police Leader Greece. Franz was promoted September 1944 to SS-Brigadeführer and Major General of the Police. As Commander of the Order Police,, he was transferred to Oslo, Norway on 7 February 1945 and remained there until the end of the war on 8 May. In Norway, he was captured by British troops. From 25 September 1945 to 1947 he was a prisoner of war in British captivity. First, starting 9 January 1946, at Island Farm Special Camp 11 from Camp 1 on the outskirts of the town of Bridgend, South Wales. Then he was transferred on 25 November 1947 to the Civil Internment Camp at Adelheide, near Delmenhorst. By December 1947 the British released him. Franz married Frida Schneider on 18 December 1917, they had no children. Hermann Franz died 18 February 1960 in Bonn at the age of 66. He wrote one book which was printed after his death:
Gebirgsjäger der Polizei. Polizei-Gebirgsjäger-Regiment 18 und Polizei-Gebirgs-Artillerieabteilung 1942–1945, Bad Nauheim, 1963.
*Translated his book tile is: Mountaineer Police. Police Mountain Infantry Regiment 18 and Police Mountain Artillery Btallion from 1942 to 1945, Publisher: Bad Nauheim in 1963.
