The unit became operational in January 1944 and participated in the arrest of French Jews, labour service evaders, and resistance members in Brittany under the leadership of the German Sicherheitsdienst (SD) secret police as well as a number of mass murders of civilians.

From August 1944, following the Allied landings in Normandy, it was gradually withdrawn easterwards into France and then Nazi Germany where it was dissolved in the aftermath of the German surrender.

Although it was gradually integrated into the French nation-state, it retained a distinct sense of ethnic and linguistic identity which was increasingly emphasised by local folklorists and historians in the 19th century.

Support was to be sought instead in the north; the Easter Rising and the Irish War of Independence were portrayed as the implementations of a successful formula that was to be emulated should France find itself in dire straits.

The incorporation of Alsace-Lorraine into France as a consequence of Germany's defeat in World War I, led to the creation of an Alsatian autonomist movement that opposed the French imposition of laïcité ("secularism").

In 1928, Breizh Atao established contacts with the Alsace-Lorraine Party, which in turn facilitated the spread of Nordism and Völkisch ideology into Breton nationalist circles.

Gwenn ha du attracted the support of many young nationalists who had become disillusioned with the failure of mainstream political parties to gain ground in formal elections.

There, he established links with Flemish nationalists, who introduced him to Gerhard von Tevenar [de], an Abwehr agent, who converted Lainé to Nordic neopaganism.

[5] Lainé returned to Brittany in 1937, relegating Gwenn ha du the responsibility of sabotage and forming Kadevernn a group that was intended to be the nucleus of a Breton national army.

Their actual mission involved establishing contact with Abwehr's Department II, which was tasked with organising subversive activities abroad.

A shipment of arms, munitions and propaganda material was delivered successfully and hidden in caches with the help of Scrignac priest Jean-Marie Perrot.

In the meantime, Breton nationalists became targets of a guerilla campaign waged by Francs-Tireurs et Partisans (FTP) who continued to view them as traitors.

[8] Lainé decided to aid the Germans in their anti-partisan operations directly, hoping for a change in policy regarding the question of Breton independence.

[9] On 11 November 1943, Lainé transformed Lu Brezon into Bezen Kadoudal, named after Georges Cadoudal, one of the leaders of the royalist Chouannerie uprising of 1794–1800.

Bezen Kadoudal was placed under the supervision of Sicherheitsdienst (SD) (S.S. Intelligence) Obersturmbannführer Hartmut Pulmer, and under the military command of Hauptscharführer Hans Grimm.

The most notable of them was a fire fight between Free French commandos and Bezen Perrot members in the vicinity of Ploërdut on 13 June which resulted in two deaths and one injury (Alan Heusaff) on the side of the collaborationists.

[15] In early August 1944, as Allied troops continued their advance from the north, Bezen Perrot was evacuated from Rennes, joining the Germans in their retreat to the east.

Lainé stayed at a farm in the vicinity of Marburg until he was provided with false papers by Celtologist Leo Weisgerber, allowing him to escape to the Republic of Ireland in 1947 where he received asylum.

[19] Still, the core members of the organisation evaded arrest, staying back in France and Germany, or fleeing to Brazil, Spain, Argentina and Ireland.

[20][18] Despite its small size, Bezen Perrot left a legacy of brutality and wartime atrocities that stigmatised the entire Breton nationalist movement.