As one of the feared V-Männer (trusted informants and undercover agents), he was directly responsible for the arrest and, in many cases, the death, of approximately 300 resistance fighters, people in hiding, downed Allied pilots, and Jews. He was known to torture prisoners personally, and he carried out executions himself on at least two occasions. De Droog’s actions led to the dismantling of many resistance groups across the country, particularly in Gelderland. He is widely regarded as one of the most notorious traitors in the Netherlands during the Second World War.