In June 1940 Paris fell to the Nazis. The occupation spelt doom and despair to many, but for some it spawned new opportunities. At the beginning of World War II, Villaplane became involved in the Parisian black market and in racketeering the local Jewish population. Through his criminal background, he came to the attention of the French Carlingue, an organisation formed by the German Reich Security Main Office to conduct counter-insurgency operations against the French Resistance. The group, which was made up of collaborating criminals, was known colloquially as the French Gestapo. It was jointly run by two Parisian gangsters, Henri Lafont and Pierre Bonny. Members utilised their criminal expertise and networks for the Nazi security services in occupied France and Vichy. Villaplane specialised in racketeering gold merchants.

Throughout 1943, French resistance to Germany intensified. The local Gestapo was ordered to help exterminate the rebels. Since Hitler had been funding an Arabic-language newspaper that depicted the Führer as the great liberator, intent on freeing downtrodden peoples from the twin evils of colonialism and communism, Lafont had the idea of reinforcing the German and collaborationist ranks by forming a squadron of fighters drawn from the immigrant population. In February 1944 the German authorities gave the go-ahead. The Brigade Nord Africain (BNA) was set up with instructions to cleanse the Périgord region. At its helm was Villaplane, promoted to the position of SS sub-lieutenant.

Villaplane's unit quickly became notorious for its cruelty. On 11 June 1944, for instance, they captured 11 resistance fighters in Mussidan, a small village in the Dordogne. Aged 17 to 26, the maquisards were marched to a ditch and shot. As well as giving the death order, Villaplane is said to have pulled one of the triggers.