For example, in 1939 Stettin and Frankfurt am Main only had a total of 41 Gestapo men combined.[98] In Düsseldorf, the local Gestapo office of only 281 men were responsible for the entire Lower Rhine region, which comprised 4 million people.[99] "V-men", as undercover Gestapo agents were known, were used to infiltrate Social Democratic and Communist opposition groups, but this was more the exception, not the rule.[100] The Gestapo office in Saarbrücken had 50 full-term informers in 1939.[100] The District Office in Nuremberg, which had the responsibility for all of northern Bavaria, employed a total of 80–100 full-term informers between 1943 and 1945.[100] The majority of Gestapo informers were not full-term informers working undercover, but were rather ordinary citizens who chose to denounce other people to the Gestapo.[101]